and controls of insurance and reinsurance companies under its jurisdiction. Furthermore, the FSA intends to place an increased emphasis on risk identification and management in relation to the prudential regulation of insurance and reinsurance business in the United Kingdom. Changes in the FSA's requirements may have an adverse impact on the business of Aspen Re.

If any entity were to hold 20% or more of the voting rights or 20% or more of the issued ordinary shares in Aspen Holdings, transactions between Aspen Re and such entity may have to be reported to the FSA if the value of those transactions exceeds certain threshold amounts that would render them material connected party transactions. In these circumstances, we cannot assure you that these material connected party transactions will not be subject to regulatory intervention by the FSA. See "Certain Relationships and Related Transactions."

Aspen Re is required to provide the FSA with information about Aspen Holdings' notional solvency, which involves calculating the solvency position of Aspen Holdings in accordance with the FSA's rules. In this regard, if Aspen Bermuda or Aspen Specialty were to experience financial difficulties, it could affect the "solvency" position of Aspen Holdings and in turn trigger regulatory intervention by the FSA with respect to Aspen Re. Furthermore, any transactions between Aspen Re, Aspen Specialty and Aspen Bermuda that are material connected party transactions would also have to be reported to the FSA. We cannot assure you that the existence or effect of such connected party transactions and the FSA's assessment of the overall solvency of Aspen Holdings and its subsidiaries, even in circumstances where Aspen Re has on its face sufficient assets of its own to cover its required margin of solvency, would not result in regulatory intervention by the FSA with regard to Aspen Re.

There may be reforms in liability insurance practice in the United Kingdom, in response to dramatic price increases that have greatly affected businesses, which may adversely impact the Company. The Office of Fair Trading ("OFT") in the United Kingdom undertook a study as a result of concerns regarding sharp increases in the cost of premiums charged for employers' public and product liability insurance and professional indemnity insurance, collectively referred to as liability insurance. The OFT has indicated that it will continue to keep liability insurance markets under review, including premiums to be charged during late 2004 and early 2005, as it anticipates the markets to have adjusted by that date. The OFT does not presently have price controls in place in relation to liability insurance. We are not aware at this time of any OFT proposals to recommend such price controls but the OFT has stated publicly that if liability insurance markets do not improve by early 2005 the OFT will consider if action is appropriate. In addition, the U.K. Department for Work and Pensions ("DWP") has conducted a specific study regarding employers' liability. Both the OFT and the DWP have focused on the potential benefit to businesses, as insureds, if insurers increased the renewal periods during which insureds can renew their insurance coverage. The OFT has the power to recommend wide ranging reforms to the extent that it finds competition has been hindered as a result of the sharp increase in premiums charged, and to refer the markets to the U.K. Competition Commission which may impose structural and behavioral remedies on the market participants. Although no particular regulatory or legislative reforms have been adopted, these reports and any subsequent regulation may adversely affect our business and results of operations. For example, if insurers were required to increase their renewal periods, this may result in increased competition to retain existing customers.

In addition, given that the framework for supervision of insurance and reinsurance companies in the United Kingdom is largely formed by E.U. directives (which are implemented by member states through national legislation), changes at the E.U. level may affect the regulatory scheme under which Aspen Re will operate. One such directive obliged the United Kingdom to ensure that, in any insolvency or reorganization proceedings concerning an insurer established in the United Kingdom, claims under insurance contracts receive priority over claims under reinsurance contracts. These rules, which were implemented into U.K. law in April 2003, may have the effect that prospective reinsureds may seek security for future claims under reinsurance policies issued by Aspen Re which would increase the cost to Aspen Re of writing reinsurance business. A general review of E.U. insurance directives is currently in progress and may lead to changes such as increased or risk-based minimum capital requirements. The FSA has proposed to introduce new Enhanced Capital Requirements

19

("ECR") for insurers and reinsurers which will include capital charges based on assets, claims and premiums. The level of ECR seems likely to be at least twice the existing required minimum solvency margin for most companies, although the FSA has already adopted an informal approach of encouraging companies to hold at least twice the current E.U. minimum. In addition, the FSA is proposing to give guidance regularly to insurers under "individual capital assessments", which may result in guidance that a company should hold in excess of the ECR. These changes may increase the required regulatory capital of Aspen Re.

Aspen Re does not presently intend that it will be admitted to do business in any jurisdiction other than the United Kingdom, Ireland and the other member states of the European Economic Area. We cannot assure you, however, that insurance regulators in the United States, Bermuda or elsewhere will not review the activities of Aspen Re and claim that Aspen Re is subject to such jurisdiction's licensing requirements.

Aspen Bermuda.    Aspen Bermuda is a registered Class 4 Bermuda insurance and reinsurance company. Among other matters, Bermuda statutes, regulations and policies of the BMA require Aspen Bermuda to maintain minimum levels of statutory capital, surplus and liquidity, to meet solvency standards, to obtain prior approval of ownership and transfer of shares and to submit to certain periodic examinations of its financial condition. These statutes and regulations may, in effect, restrict Aspen Bermuda's ability to write insurance and reinsurance policies, to make certain investments and to distribute funds.

Aspen Bermuda does not maintain a principal office, and its personnel do not solicit, advertise, settle claims or conduct other activities that may constitute the transaction of the business of insurance or reinsurance, in any jurisdiction in which it is not licensed or otherwise not authorized to engage in such activities. Although Aspen Bermuda does not believe it is or will be in violation of insurance laws or regulations of any jurisdiction outside Bermuda, inquiries or challenges to Aspen Bermuda's insurance or reinsurance activities may still be raised in the future.

The offshore insurance and reinsurance regulatory environment has become subject to increased scrutiny in many jurisdictions, including the United States and various states within the United States. Compliance with any new laws or regulations regulating offshore insurers or reinsurers could have a material adverse effect on our business.

Aspen Specialty.    Aspen Specialty is organized in and has received a license to write certain lines of insurance business in the State of North Dakota and, as a result, is subject to North Dakota law and regulation under the supervision of the Commissioner of Insurance of the State of North Dakota. The North Dakota Commissioner of Insurance also has regulatory authority over a number of affiliate transactions between Aspen Specialty and other members of our holding company system. The purpose of the state insurance regulatory statutes is to protect U.S. insureds and U.S. ceding insurance companies, not our shareholders or noteholders. Among other matters, state insurance regulations will require Aspen Specialty to maintain minimum levels of capital, surplus and liquidity, require Aspen Specialty to comply with applicable risk-based capital requirements and will impose restrictions on the payment of dividends and distributions. These statutes and regulations may, in effect, restrict the ability of Aspen Specialty to write new business or distribute assets to Aspen Holdings.

In recent years, the U.S. insurance regulatory framework has come under increased federal scrutiny, and some state legislators have considered or enacted laws that may alter or increase state regulation of insurance and reinsurance companies and holding companies. Moreover, the NAIC, which is an association of the insurance commissioners of all 50 states and the District of Columbia, and state insurance regulators regularly examine existing laws and regulations. Changes in these laws and regulations or the interpretation of these laws and regulations could have a material adverse effect on our business.

For example, in response to the tightening of supply in certain insurance and reinsurance markets resulting from, among other things, the World Trade Center tragedy, the Terrorism Risk Insurance Act of 2002 (the "Terrorism Act") was enacted to ensure the availability of insurance coverage for

20

---

terrorist acts in the United States. This law establishes a federal assistance program through the end of 2005 to help the commercial property and casualty insurance industry cover claims related to future terrorism related losses and regulates the terms of insurance relating to terrorism coverage. Although competing bills to extend the Terrorism Act beyond 2005 have recently been introduced in the U.S. Congress, we are currently unable to predict whether the Terrorism Act will lapse, be renewed or replaced by something else in 2005, or whether any new initiatives would result in greater federal government intervention in the U.S. insurance and reinsurance markets in which we participate.

New laws and regulations or changes in existing laws and regulations or the interpretation of these laws and regulations could have a material adverse effect on our business or results of operations. For example, a bill now pending in the U.S. Congress would limit the liability of certain defendants who have asbestos liabilities, but would also require defendants and insurers to contribute to a trust fund to compensate persons alleging to have been harmed by asbestos exposure. To the extent that the passage of such legislation might provide our competitors with somewhat greater certainty as to their ultimate asbestos liabilities, some of their current reserves might be released, thus providing them additional underwriting capacity. This, in turn, could result in increased competitive pressure on us. However, because prospects for passage of this bill as well as its details (the trust fund provisions in particular) are uncertain, we cannot at this time predict how the passage of such legislation might impact us.

Our ability to pay dividends or to meet ongoing cash requirements may be constrained by our holding company structure.

We are a holding company and, as such, have no substantial operations of our own. We do not expect to have any significant operations or assets other than our ownership of the shares of our Insurance Subsidiaries. Dividends and other permitted distributions from our Insurance Subsidiaries are expected to be our sole source of funds to meet ongoing cash requirements, including any future debt service payments and other expenses, and to pay dividends, if any, to our shareholders. Our Insurance Subsidiaries are subject to significant regulatory restrictions limiting their ability to declare and pay dividends. The inability of our Insurance Subsidiaries to pay dividends in an amount sufficient to enable us to meet our cash requirements at the holding company level could have a material adverse effect on our business. See "Regulatory Matters — Bermuda Regulation — Minimum Solvency Margin and Restrictions on Dividends and Distributions," "— U.K. Regulation — Restrictions on Dividend Payments," and "— U.S. Regulation — North Dakota State Dividend Limitations."

Certain regulatory and other constraints may limit our ability to pay dividends.

We are subject to Bermuda regulatory constraints that will affect our ability to pay dividends on our ordinary shares and make other payments. Under the Bermuda Companies Act 1981, as amended (the "Companies Act"), we may declare or pay a dividend out of distributable reserves only if we have reasonable grounds to believe that we are, and would after the payment be, able to pay our liabilities as they become due and if the realizable value of our assets would thereby not be less than the aggregate of our liabilities and issued share capital and share premium accounts. In addition, our ability to pay dividends to our shareholders is limited under our Credit Agreements (as defined in "Management's Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources"), which provide that, subject to the requirements specified in the agreements, Aspen Holdings may not during any fiscal year pay cash dividends in an aggregate amount exceeding 50% of its consolidated net income for such fiscal year. If you require dividend income you should carefully consider these risks before investing in our Company. For more information regarding restrictions on the payment of dividends by us and our Insurance Subsidiaries, see "Dividend Policy," "Regulatory Matters" and "Management's Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources."

21

---

Several of our founding shareholders and some of our directors may have conflicts of interest with us.

Several of our founding shareholders and some of our directors engage in commercial activities and enter into transactions or agreements with us or in competition with us, which may give rise to conflicts of interest. Of our directors, Julian Avery was the Chief Executive Officer of Wellington until his resignation effective September 20, 2004. We had in place certain quota share agreements under our framework agreement which may be entered into through 2005 and an administrative services agreement with Wellington and its affiliates for which we have received notice of termination in December 2003, with termination effective 18 months from the date of notice. We also have entered into an IT services agreement with Wellington and its affiliates for which we have provided a notice of termination on August 20, 2004, with termination being effective on August 20, 2005, subject to certain transition services. We also had an agreement with Montpelier Re, one of our founding shareholders, which in 2003 limited the type and the amount of business we could write in Bermuda. Montpelier Re is also a competitor of ours in the reinsurance business. See "Certain Relationships and Related Transactions — Transactions and Relationships with Initial Investors."

In addition, several of our founding shareholders and some of our directors have sponsored or invested in, and may in the future sponsor or invest in, other entities engaged in or intending to engage in insurance and reinsurance underwriting, some of which may compete with us. They have also entered into, or may in the future enter into, agreements with companies that may compete with us. We do not have any agreement or understanding with any of these parties regarding the resolution of potential conflicts of interest.

In addition, we may not be in a position to influence any party's decision to engage in activities that would give rise to a conflict of interest. These parties may take actions that are not in our shareholders' best interests. See "Business — Reinsurance" and "Certain Relationships and Related Transactions." Moreover, under Bermuda law and our bye-laws, any transaction entered into by us in which a director has an interest is not voidable by us nor can such director be accountable to us for any benefit realized under that transaction provided that the nature of the interest is disclosed at the first opportunity at a meeting of directors, or in writing to the directors. In addition, our bye-laws allow a director to be taken into account in determining whether a quorum is present and to vote on a transaction in which he has an interest unless the majority of the disinterested directors determines otherwise.

We may experience difficulty in attracting and retaining qualified independent directors in the
increasingly regulated corporate governance environment.

We are subject to the independent director requirements of the Sarbanes-Oxley Act of 2002 (the "Sarbanes-Oxley Act"), SEC rules and the NYSE corporate governance rules, to the extent applicable. The Company has a sufficient number of independent directors to comply with such rules applicable to the audit committee. The Company does not currently have a sufficient number of independent directors to comply with the requirements for independent nomination and compensation committees, although such rules allow a phase-in period of twelve months for newly listed companies such as us and are not strictly applicable to us so long as we remain qualified as a foreign private issuer. Independent directors are generally individuals, other than our employees, officers or their family members or shareholders who hold more than a 10% interest in us, who do not have a material relationship with us and have not received certain compensation or other payments from us in previous years. The ultimate determination of independence, however, is made by our board of directors on a case-by-case basis based on all relevant facts and circumstances.

We may experience difficulty in attracting and retaining qualified independent directors to respond to the increasing regulation of public companies. If we are unable to attract or retain independent directors prior to the compliance deadlines stipulated by the various regulations, we may be faced with delisting of our ordinary shares or a violation of the Sarbanes-Oxley Act.

22

---

We may require additional capital in the future, which may not be available or may only be available on unfavorable terms.

Our future capital requirements depend on many factors, including our ability to write new business successfully and to establish premium rates and reserves at levels sufficient to cover losses. To the extent that our funds are insufficient to fund future operating requirements and/or cover claim losses, we may need to raise additional funds through financings or curtail our growth and reduce our assets. Our additional needs for capital will depend on our actual claims experience, especially any catastrophic events. Any equity or debt financing, if available at all, may be on terms that are not favorable to us. If we cannot obtain adequate capital on favorable terms or at all, our business, operating results and financial condition could be adversely affected.

Risks Related to Our Industry

We operate in a highly competitive environment, and substantial new capital inflows into the
insurance and reinsurance industry will increase competition.

The insurance and reinsurance industry is highly competitive. In particular, we compete with General Re, Lloyd's, Montpelier Re, Munich Re, Swiss Re and XL Re in the global reinsurance industry and with Lloyd's, Mitsui, Royal & Sun Alliance and Zurich in the U.K. insurance industry. See "Business — Competition" for a more comprehensive list of our competitors. We compete primarily on the basis of experience, the strength of our client relationships, reputation, premiums charged, policy and contract terms and conditions, products offered, speed of claims payment, overall financial strength, ratings and scope of business (both by size and geographic location).

A number of newly-organized, Bermuda-based insurance and reinsurance entities compete in the same market segments in which we operate. Many of these entities derive their profits primarily through Bermuda operations and, consequently, may achieve a lower overall global effective tax rate than us. In addition, we may not be aware of other companies that may be planning to enter the lines of business of the insurance and reinsurance market in which we operate or of existing companies that may be planning to raise additional capital.

Increased competition could result in fewer submissions, lower premium rates and less favorable policy terms and conditions, which could have a material adverse impact on our growth and profitability. We have recently experienced increased competition in some lines of business which has caused a decline in rate increases or a reduction in rates.

Further, insurance/risk-linked securities and derivatives and other non-traditional risk transfer mechanisms and vehicles are being developed and offered by other parties, including non-insurance company entities, which could impact the demand for traditional insurance and reinsurance. A number of new, proposed or potential legislative or industry developments could also increase competition in our industries.

New competition could cause the demand for insurance or reinsurance to fall or the expense of customer acquisition and retention to increase, either of which could have a material adverse effect on our growth and profitability.

Recent events may result in political, regulatory and industry initiatives which could adversely affect our business.

The supply of insurance and reinsurance coverage has decreased due to withdrawal of capacity and substantial reductions in capital resulting from, among other things, the terrorist attacks of September 11, 2001. This tightening of supply has resulted in governmental intervention in the insurance and reinsurance markets, both in the United States and worldwide. For example, on November 26, 2002, the Terrorism Act was enacted to ensure the availability of insurance coverage for terrorist acts in the United States. This law requires insurers writing certain lines of property and casualty insurance to offer coverage against certain acts of terrorism causing damage within the United States or to U.S. flagged vessels or aircraft. In return, the law requires the federal government

23

---

to indemnify such insurers for 90% of insured losses resulting from covered acts of terrorism, subject to a premium-based deductible. Although competing bills to extend the Terrorism Act beyond 2005 have recently been introduced in the U.S. Congress, the law is currently scheduled to expire automatically at the end of 2005 and we cannot predict whether it will lapse, be renewed or replaced by something else. See "Regulatory Matters — U.S. Regulation — Legislative Changes." Government-sponsored initiatives in other countries to address the risk of losses from terrorist attacks are similarly subject to change which may impact our business. We are currently unable to predict the extent to which lapse or replacement of the Terrorism Act, or other new initiatives, may affect the demand for or pricing of our products or the risks that our customers may expect us, and our competitors, to underwrite.

The insurance and reinsurance business is historically cyclical and we expect to experience periods with excess underwriting capacity and unfavorable premium rates.

Historically, insurers and reinsurers have experienced significant fluctuations in operating results due to competition, frequency of occurrence or severity of catastrophic events, levels of capacity, general economic conditions and other factors. The supply of insurance and reinsurance is related to prevailing prices, the level of insured losses and the level of industry surplus which, in turn, may fluctuate in response to changes in rates of return on investments being earned in the insurance and reinsurance industry. As a result, the insurance and reinsurance business historically has been a cyclical industry characterized by periods of intense price competition due to excessive underwriting capacity as well as periods when shortages of capacity permitted favorable premium levels. The supply of insurance and reinsurance may increase, either by capital provided by new entrants or by the commitment of additional capital by existing insurers or reinsurers, which may cause prices to decrease. Although premium levels for many products have increased in the recent past, there are several lines of business in which rates are stablizing or declining which, absent a major industry event, may indicate a change in the cycle. In respect of current market conditions, there have been some rate reductions in property lines and a slowing of rate increases in casualty lines. Any of these factors could lead to a significant reduction in premium rates, less favorable policy terms and fewer submissions for our underwriting services. In addition to these considerations, changes in the frequency and severity of losses suffered by insureds and insurers may affect the cycles of the insurance and reinsurance business significantly, and we expect to experience the effects of such cyclicality.

Risks Related to Our Ordinary Shares and This Offering

Future sales of ordinary shares may affect their market price and the future exercise of options may result in immediate and substantial dilution.

As of September 1, 2004, there were 69,174,303 ordinary shares outstanding. Of these shares, 12,102,600 ordinary shares are freely transferable, except for any shares sold to our "affiliates," as that term is defined in Rule 144 under the Securities Act. Substantially all of our remaining ordinary shares may not be sold in the absence of registration under the Securities Act unless an exemption from registration is available, including the exemptions contained in Rule 144. Under Rule 144(k), a person who is not our affiliate, and who has not been our affiliate at any time during the 90 days preceding any sale, is entitled to sell the shares without regard to the foregoing limitations, provided that at least two years have elapsed since the shares were acquired from us or any affiliate of ours. A large percentage of our initial investors have held a portion of our ordinary shares for at least two years, although some of those investors may be deemed our affiliates. Moreover, as of September 1, 2004, an additional 6,347,736 ordinary shares were issuable upon the full exercise of outstanding options by Wellington (the "Wellington Options") and Harrington Trust Limited, which name was changed to Appleby Trust (Bermuda) Limited effective October 1, 2004 (the "Names' Trustee"), as successor trustee of the Names' Trust (the "Names' Trust"), which holds the options (the "Names' Options"; collectively with the Wellington Options, the "Investor Options") and shares for the benefit of the members of Syndicate 2020 who are not corporate members of Wellington (the "Unaligned Members"). Wellington and the Names' Trustee may exercise their options on a cashless basis, which

24

---

allows them to realize the economic benefit of the difference between the subscription price under the options and the then prevailing market price without having to pay the subscription price for any such ordinary shares in cash. Thus, the option holder receives fewer shares upon exercise. Ordinary shares issued upon the exercise of options on a cashless basis will be issued as a bonus issue of shares in accordance with section 40(2)(a) of the Companies Act. This section provides that the share premium account of a company may be applied in paying up shares issued to shareholders as fully paid shares. This cashless exercise feature may provide an incentive for Wellington and the Names' Trustee to exercise their options more quickly. In the event that the outstanding options to purchase ordinary shares are exercised, you will suffer immediate and substantial dilution of your investment.

In addition, we have filed a registration statement on Form S-8 under the Securities Act to register ordinary shares issued or reserved for issuance under our share incentive plan. Subject to the exercise of issued and outstanding options and shareholder agreements between the Company and individual employees, shares registered under the registration statement on Form S-8 may be available for sale into the public markets.

We cannot predict what effect, if any, future sales of our ordinary shares, or the availability of ordinary shares for future sale, will have on the market price of our ordinary shares. Sales of substantial amounts of our ordinary shares in the public market, or the perception that these sales could occur, could adversely affect the market price of our ordinary shares. See "Description of Share Capital — Registration Rights Agreement" and "Shares Eligible for Future Sale" for further information regarding circumstances under which ordinary shares may be sold.

There are provisions in our charter documents which may reduce or increase the voting rights of our ordinary shares.

In general, and except as provided below, shareholders have one vote for each ordinary share held by them and are entitled to vote at all meetings of shareholders. However, if, and so long as, the ordinary shares of a shareholder are treated as "controlled shares" (as determined under section 958 of the Internal Revenue Code of 1986, as amended (the "Code")) of any U.S. Person (as defined in "Material Tax Considerations — Taxation of Shareholders — United States Taxation" and such controlled shares constitute 9.5% or more of the votes conferred by our issued shares, the voting rights with respect to the controlled shares of such U.S. Person (a "9.5% U.S. Shareholder") shall be limited, in the aggregate, to a voting power of less than 9.5%, under a formula specified in our bye-laws. The formula is applied repeatedly until the voting power of all 9.5% U.S. Shareholders has been reduced to less than 9.5%. In addition, our board of directors may limit a shareholder's voting rights where it deems it appropriate to do so to (i) avoid the existence of any 9.5% U.S. Shareholder; and (ii) avoid certain material adverse tax, legal or regulatory consequences to us or any of our subsidiaries or any shareholder or its affiliates. "Controlled shares" includes, among other things, all shares of the Company that such U.S. Person is deemed to own directly, indirectly or constructively (within the meaning of section 958 of the Code). As of September 1, 2004, there were 69,174,303 ordinary shares outstanding, of which 6,571,558 ordinary shares would constitute 9.5% of the votes conferred by our issued and outstanding shares. A shareholder may own up to 6,571,558 ordinary shares without being subject to voting cutback provisions in our bye-laws.

Under these provisions, certain shareholders may have their voting rights limited to less than one vote per share, while other shareholders may have voting rights in excess of one vote per share. See "Description of Share Capital — Bye-Laws". Moreover, these provisions could have the effect of reducing the votes of certain shareholders who would not otherwise be subject to the 9.5% limitation by virtue of their direct share ownership. Our bye-laws provide that shareholders will be notified of their voting interests prior to any vote to be taken by them. See "Description of Share Capital — Voting Adjustments".

As a result of any reallocation of votes, voting rights of some of our shareholders might increase above 5% of the aggregate voting power of the outstanding ordinary shares, thereby possibly resulting in such shareholders becoming a reporting person subject to Schedule 13D or 13G filing requirements

25

---

under the Securities Exchange Act of 1934 (the "Exchange Act"). In addition, the reallocation of the votes of our shareholders could result in some of the shareholders becoming subject to filing requirements under Section 16 of the Exchange Act in the event that the Company no longer qualifies as a foreign private issuer.

We also have the authority under our bye-laws to request information from any shareholder for the purpose of determining whether a shareholder's voting rights are to be reallocated under the bye-laws. If a shareholder fails to respond to our request for information or submits incomplete or inaccurate information in response to a request by us, we may, in our sole discretion, eliminate such shareholder's voting rights.

There are provisions in our bye-laws which may restrict the ability to transfer ordinary shares and which may require shareholders to sell their ordinary shares.

Our board of directors may decline to register a transfer of any ordinary shares if it appears to the board of directors, in their sole and reasonable discretion, after taking into account the limitations on voting rights contained in our bye-laws, that any non-de minimis adverse tax, regulatory or legal consequences to us, any of our subsidiaries or any of our shareholders or their affiliates may occur as a result of such transfer.

Our bye-laws also provide that if our board of directors determines that share ownership by a person may result in material adverse tax consequences to us, any of our subsidiaries or any shareholder or its affiliates, then we have the option, but not the obligation, to require that shareholder to sell to us or to third parties to whom we assign the repurchase right for fair market value the minimum number of ordinary shares held by such person which is necessary to eliminate the material adverse tax consequences. See "Description of Share Capital — Acquisition of Ordinary Shares by the Company."

Laws and regulations of the jurisdictions where we conduct business could delay or deter a takeover attempt that shareholders might consider to be desirable and may make it more difficult to replace members of our board of directors and have the effect of entrenching management.

Ordinary shares may be offered or sold in Bermuda only in compliance with the provisions of the Investment Business Act 2003 of Bermuda which regulates the sale of securities in Bermuda. In addition, the BMA must approve all issuances and transfers of shares of a Bermuda exempted company. We have obtained from the BMA their permission for the issue and free transferability of the ordinary shares in the Company being offered pursuant to this prospectus, as long as the shares are listed on the NYSE or other appointed stock exchange, to and among persons who are non-residents of Bermuda for exchange control purposes and of up to 20% of the ordinary shares to and among persons who are residents in Bermuda for exchange control purposes. The BMA and the Registrar of Companies accept no responsibility for the financial soundness of any proposal or for the correctness of any of the statements made or opinions expressed in this prospectus.

The FSA regulates the acquisition of "control" of any U.K. insurance company authorized under the Financial Services and Markets Act of 2000 ("FSMA"). Any company or individual that (together with its or his associates) directly or indirectly acquires 10% or more of the shares of a U.K. authorized insurance company or its parent company, or is entitled to exercise or control the exercise of 10% or more of the voting power in such authorized insurance company or its parent company, would be considered to have acquired "control" for the purposes of FSMA, as would a person who had significant influence over the management of such authorized insurance company or its parent company by virtue of his shareholding or voting power in either. A purchaser of 10% or more of our ordinary shares would therefore be considered to have acquired "control" of Aspen Re. Under FSMA, any person proposing to acquire "control" over a U.K. authorized insurance company must notify the FSA of his intention to do so and obtain the FSA's prior approval. The FSA would then have three months to consider that person's application to acquire "control." In considering whether to approve such application, the FSA must be satisfied both that the acquirer is a fit and proper

26

---

person to have such "control" and that the interests of consumers would not be threatened by such acquisition of "control." Failure to make the relevant prior application would constitute a criminal offense.

There can be no assurance that the applicable regulatory body would agree that a shareholder who owned greater than 10% of our ordinary shares did not, because of the limitation on the voting power of such shares, control the applicable Insurance Subsidiary.

These laws may discourage potential acquisition proposals and may delay, deter or prevent a change of control of our company, including through transactions, and in particular unsolicited transactions, that some or all of our shareholders might consider to be desirable. These restrictions may also operate to make it more difficult to replace members of our board of directors and may have the effect of entrenching management regardless of their performance.

A few large shareholders may be able to influence significant corporate actions.

We currently have 5 shareholder groups who own approximately 51,024,280 ordinary shares representing approximately 70% of the beneficial ownership of our ordinary shares (assuming full exercise on a cash basis of Wellington Options). As a result of their ownership position, these shareholders voting together may have the ability to significantly influence matters requiring shareholder approval, including, without limitation, the election of directors and amalgamations, consolidations, changes of control of our company and sales of all or substantially all of our assets. If these shareholders were to act together, they would be able to exercise control over most matters requiring approval by our shareholders, including the election of directors and approval of significant corporate transactions. These actions may be taken even if they are opposed by the other shareholders.

U.S. persons who own our ordinary shares may have more difficulty in protecting their interests than U.S. persons who are shareholders of a U.S. corporation.

The Companies Act, which applies to us, differs in some material respects from laws generally applicable to U.S. corporations and their shareholders. Set forth below is a summary of certain significant provisions of the Companies Act which includes, where relevant, information on modifications thereto adopted under our bye-laws, applicable to us, which differ in certain respects from provisions of Delaware corporate law (which is representative of the corporate law of the various states comprising the United States). Because the following statements are summaries, they do not discuss all aspects of Bermuda law that may be relevant to us and our shareholders.

Interested Directors.    Under Bermuda law and our bye-laws, a transaction entered into by us, in which a director has an interest, will not be voidable by us, and such director will not be accountable to us for any benefit realized under that transaction, provided the nature of the interest is disclosed at the first opportunity at a meeting of directors, or in writing, to the directors. In addition, our bye-laws allow a director to be taken into account in determining whether a quorum is present and to vote on a transaction in which that director has an interest following a declaration of the interest under the Companies Act, unless the majority of the disinterested directors determine otherwise. Under Delaware law, the transaction would not be voidable if:

•	the material facts as to the interested director's relationship or interests were disclosed or were known to the board of directors and the board of directors in good faith authorized the transaction by the affirmative vote of a majority of the disinterested directors;

•	the material facts were disclosed or were known to the shareholders entitled to vote on such transaction and the transaction was specifically approved in good faith by vote of the majority of shares entitled to vote thereon; or

•	the transaction was fair as to the corporation at the time it was authorized, approved or ratified.

Business Combinations with Large Shareholders or Affiliates.    As a Bermuda company, we may enter into business combinations with our large shareholders or one or more wholly-owned

27

---

subsidiaries, including asset sales and other transactions in which a large shareholder or a wholly-owned subsidiary receives, or could receive, a financial benefit that is greater than that received, or to be received, by other shareholders or other wholly-owned subsidiaries, without obtaining prior approval from our shareholders and without special approval from our board of directors. Under Bermuda law, amalgamations require the approval of the board of directors, and except in the case of amalgamations with and between wholly-owned subsidiaries, shareholder approval. However, when the affairs of a Bermuda company are being conducted in a manner which is oppressive or prejudicial to the interests of some shareholders, one or more shareholders may apply to a Bermuda court, which may make an order as it sees fit, including an order regulating the conduct of the company's affairs in the future or ordering the purchase of the shares of any shareholders by other shareholders or the company. If we were a Delaware company, we would need prior approval from our board of directors or a supermajority of our shareholders to enter into a business combination with an interested shareholder for a period of three years from the time the person became an interested shareholder, unless we opted out of the relevant Delaware statute. Bermuda law or our bye-laws would require board approval and, in some instances, shareholder approval of such transactions.

Shareholders' Suits.    The rights of shareholders under Bermuda law are not as extensive as the rights of shareholders in many U.S. jurisdictions. Class actions and derivative actions are generally not available to shareholders under the laws of Bermuda. However, the Bermuda courts ordinarily would be expected to follow English case law precedent, which would permit a shareholder to commence a derivative action in our name to remedy a wrong done to us where an act is alleged to be beyond our corporate power, is illegal or would result in the violation of our memorandum of association or bye-laws. Furthermore, consideration would be given by the court to acts that are alleged to constitute a fraud against the minority shareholders or where an act requires the approval of a greater percentage of our shareholders than actually approved it. The winning party in such an action generally would be able to recover a portion of attorneys' fees incurred in connection with the action. Our bye-laws provide that shareholders waive all claims or rights of action that they might have, individually or in the right of the Company, against any director or officer for any act or failure to act in the performance of such director's or officer's duties, except with respect to any fraud of the director or officer or to recover any gain, personal profit or advantage to which the director or officer is not legally entitled. Class actions and derivative actions generally are available to shareholders under Delaware law for, among other things, breach of fiduciary duty, corporate waste and actions not taken in accordance with applicable law. In such actions, the court has discretion to permit the winning party to recover attorneys' fees incurred in connection with the action.

Indemnification of Directors and Officers.    Under Bermuda law and our bye-laws, we may indemnify our directors, officers, any other person appointed to a committee of the board of directors or resident representative (and their respective heirs, executors or administrators) to the full extent permitted by law against all actions, costs, charges, liabilities, loss, damage or expense, incurred or suffered by such persons by reason of any act done, conceived in or omitted in the conduct of our business or in the discharge of their duties; provided that such indemnification shall not extend to any matter which would render such indemnification void under the Companies Act. Under Delaware law, a corporation may indemnify a director or officer of the corporation against expenses (including attorneys' fees), judgments, fines and amounts paid in settlement actually and reasonably incurred in defense of an action, suit or proceeding by reason of such position if (i) such director or officer acted in good faith and in a manner he reasonably believed to be in or not opposed to the best interests of the corporation and (ii) with respect to any criminal action or proceeding, such director or officer had no reasonable cause to believe his conduct was unlawful.

To further understand the risks associated with U.S. persons who own our ordinary shares, see "Description of Share Capital — Differences in Corporate Law" for more information on the differences between Bermuda and Delaware corporate laws.

28

---

Anti-takeover provisions in our bye-laws could impede an attempt to replace or remove our directors, which could diminish the value of our ordinary shares.

Our bye-laws contain provisions that may entrench directors and make it more difficult for shareholders to replace directors even if the shareholders consider it beneficial to do so. In addition, these provisions could delay or prevent a change of control that a shareholder might consider favorable. For example, these provisions may prevent a shareholder from receiving the benefit from any premium over the market price of our ordinary shares offered by a bidder in a potential takeover. Even in the absence of an attempt to effect a change in management or a takeover attempt, these provisions may adversely affect the prevailing market price of our ordinary shares if they are viewed as discouraging changes in management and takeover attempts in the future.

For example, our bye-laws contain the following provisions that could have such an effect:

•	election of directors is staggered, meaning that members of only one of three classes of directors are elected each year;

•	directors serve for a term of three years;

•	our directors may decline to approve or register any transfer of shares to the extent they determine, in their sole discretion, that any non-de minimis adverse tax, regulatory or legal consequences to Aspen Holdings, any of its subsidiaries, shareholders or affiliates would result from such transfer;

•

if our directors determine that share ownership by any person may result in material adverse tax consequences to Aspen Holdings, any of its subsidiaries, shareholders or affiliates, we have the option, but not the obligation, to purchase or assign to a third party the right to purchase the minimum number of shares held by such person solely to the extent that it is necessary to eliminate such material risk;

•	shareholders have limited ability to remove directors; and

•	if the ordinary shares of any U.S. Person constitute 9.5% or more of the votes conferred by the issued shares of Aspen Holdings, the voting rights with respect to the controlled shares of such U.S. Person shall be limited, in the aggregate, to a voting power of less than 9.5%.

In addition, none of the seats on our board of directors may be up for election until 2005. As the shareholders may not be able to elect directors in the interim, this may further impede an attempt to replace or remove our directors and, consequently, diminish the value of our ordinary shares.

We are a Bermuda company and it may be difficult for you to enforce judgments against us or our directors and executive officers.

We are incorporated under the laws of Bermuda and our business is based in Bermuda. In addition, certain of our directors and officers reside outside the United States, and a substantial portion of our assets and the assets of such persons are located in jurisdictions outside the United States. As such, it may be difficult or impossible to effect service of process within the United States upon us or those persons or to recover against us or them on judgments of U.S. courts, including judgments predicated upon civil liability provisions of the U.S. federal securities laws. Further, no claim may be brought in Bermuda against us or our directors and officers in the first instance for violation of U.S. federal securities laws because these laws have no extraterritorial jurisdiction under Bermuda law and do not have force of law in Bermuda. A Bermuda court may, however, impose civil liability, including the possibility of monetary damages, on us or our directors and officers if the facts alleged in a complaint constitute or give rise to a cause of action under Bermuda law.

We have been advised by Bermuda counsel, that there is no treaty in force between the U.S. and Bermuda providing for the reciprocal recognition and enforcement of judgments in civil and commercial matters. As a result, whether a U.S. judgment would be enforceable in Bermuda against us or our directors and officers depends on whether the U.S. court that entered the judgment is recognized by the Bermuda court as having jurisdiction over us or our directors and officers, as

29

---

determined by reference to Bermuda conflict of law rules. A judgment debt from a U.S. court that is final and for a sum certain based on U.S. federal securities laws will not be enforceable in Bermuda unless the judgment debtor had submitted to the jurisdiction of the U.S. court, and the issue of submission and jurisdiction is a matter of Bermuda (not U.S.) law.

In addition to and irrespective of jurisdictional issues, the Bermuda courts will not enforce a U.S. federal securities law that is either penal or contrary to public policy. It is the advice of our Bermuda counsel that an action brought pursuant to a public or penal law, the purpose of which is the enforcement of a sanction, power or right at the instance of the state in its sovereign capacity, will not be entertained by a Bermuda Court. Certain remedies available under the laws of U.S. jurisdictions, including certain remedies under U.S. federal securities laws, would not be available under Bermuda law or enforceable in a Bermuda court, as they would be contrary to Bermuda public policy. Further, no claim may be brought in Bermuda against us or our directors and officers in the first instance for violation of U.S. federal securities laws because these laws have no extraterritorial jurisdiction under Bermuda law and do not have force of law in Bermuda. A Bermuda court may, however, impose civil liability on us or our directors and officers if the facts alleged in a complaint constitute or give rise to a cause of action under Bermuda law.

Risks Related to Taxation

We may become subject to taxes in Bermuda after March 28, 2016, which may have a material
adverse effect on our results of operations.

The Bermuda Minister of Finance, under the Exempted Undertakings Tax Protection Act 1966, as amended, of Bermuda, has given each of Aspen Holdings and Aspen Bermuda an assurance that if any legislation is enacted in Bermuda that would impose tax computed on profits or income, or computed on any capital asset, gain or appreciation, or any tax in the nature of estate duty or inheritance tax, then the imposition of any such tax will not be applicable to Aspen Holdings, Aspen Bermuda or any of their respective operations, shares, debentures or other obligations until March 28, 2016. See "Material Tax Considerations—Taxation of Aspen Holdings and Subsidiaries — Bermuda." Given the limited duration of the Minister of Finance's assurance, we cannot be certain that we will not be subject to any Bermuda tax after March 28, 2016.

Our non-U.S. companies may be subject to U.S. tax that may have a material adverse effect on our results of operations and your investment.

If Aspen Holdings or any of its foreign subsidiaries were considered to be engaged in a trade or business in the United States, it could be subject to U.S. corporate income and additional branch profits taxes on the portion of its earnings effectively connected to such U.S. business, in which case its results of operations could be materially adversely affected (although its results of operations should not be materially adversely affected if Aspen Re is considered to be engaged in a U.S. trade or business solely as a result of the binding authorities granted to Aspen Re America, Aspen Management and Wellington Underwriting, Inc. ("WU Inc.")). Further, if we or any of our subsidiaries were considered a personal holding company ("PHC") subject to U.S. tax on a portion of its U.S. income, its results of operations could be materially adversely affected.

Aspen Holdings and Aspen Bermuda are Bermuda companies, and Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services are U.K. companies. We intend to manage our business so that each of these companies will operate in such a manner that none of these companies will be subject to U.S. tax (other than U.S. excise tax on insurance and reinsurance premium income attributable to insuring or reinsuring U.S. risks and U.S. withholding tax on certain U.S. source investment income and the likely imposition of U.S. corporate income and additional branch profits tax on the profits attributable to the business of Aspen Re produced pursuant to the binding authorities granted to Aspen Re America and Aspen Management, as well as the binding authorities previously granted to WU Inc.) because none of these companies should be treated as engaged in a trade or business within the United States (other than Aspen Re with respect to the business produced pursuant to the Aspen Re America, Aspen Management and prior WU Inc. binding authorities agreements). However, because

30

---

there is considerable uncertainty as to the activities which constitute being engaged in a trade or business within the United States, we cannot be certain that the U.S. Internal Revenue Service ("IRS") will not contend successfully that any of Aspen Holdings or its foreign subsidiaries is/are engaged in a trade or business in the United States based on activities in addition to the binding authorities discussed above. See "Material Tax Considerations — Taxation of Aspen Holdings and Subsidiaries — United States."

Aspen Holdings or a subsidiary might be subject to U.S. tax on a portion of its U.S. income if Aspen Holdings or such subsidiary is considered a PHC for U.S. federal income tax purposes. This status will depend on whether more than 50% of our shares could be deemed to be owned (pursuant to certain constructive ownership rules) by five or fewer individuals and whether 60% or more of Aspen Holdings' income, or the income of any of its subsidiaries, as determined for U.S. federal income tax purposes, consists of "personal holding company income." We believe based upon the information made available to us regarding our existing shareholder base that neither the Company nor any of its subsidiaries should be considered a PHC for U.S. federal income tax purposes for any prior year of operations or currently. Additionally, we intend to manage our business to minimize the possibility that we will meet the 60% income threshold so that neither Aspen Holdings nor any of its subsidiaries should be considered a PHC. However, because of the legal and factual uncertainties regarding the application of the constructive ownership rules, the makeup of our shareholder base, our gross income and other circumstances, we cannot be certain that the Company and/or any of its subsidiaries will not be considered a PHC or that the amount of U.S. tax that would be imposed if the Company and/or any of its subsidiaries were a PHC would be immaterial. See "Material Tax Considerations — Taxation of Aspen Holdings and Subsidiaries — United States — Personal Holding Companies."

Our non-U.K. companies may be subject to U.K. tax that may have a material adverse effect on our results of operations.

None of us, except for Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services, is incorporated in the United Kingdom. Accordingly, none of us, other than Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services, should be treated as being resident in the United Kingdom for corporation tax purposes unless our central management and control is exercised in the United Kingdom. The concept of central management and control is indicative of the highest level of control of a company, which is wholly a question of fact. Each of us, other than Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services, intends to manage our affairs so that none of us, other than Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services, is resident in the United Kingdom for tax purposes.

A company not resident in the United Kingdom for corporation tax purposes can nevertheless be subject to U.K. corporation tax if it carries on a trade through a permanent establishment in the United Kingdom but the charge to U.K. corporation tax is limited to profits (including revenue profits and capital gains) attributable directly or indirectly to such permanent establishment.

Each of us, other than Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services (which should be treated as resident in the United Kingdom by virtue of being incorporated and managed there), intends that we will operate in such a manner so that none of us, other than Aspen Re and Aspen U.K. Services, carries on a trade through a permanent establishment in the United Kingdom. Nevertheless, because neither case law nor U.K. statute definitively defines the activities that constitute trading in the United Kingdom through a permanent establishment, the U.K. Inland Revenue might contend successfully that any of us, other than Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services, are/is trading in the United Kingdom through a permanent establishment in the United Kingdom.

The United Kingdom has no income tax treaty with Bermuda. There are circumstances in which companies that are neither resident in the United Kingdom nor entitled to the protection afforded by a double tax treaty between the United Kingdom and the jurisdiction in which they are resident may be exposed to income tax in the United Kingdom (other than by deduction or withholding) on the

31

---

profits of a trade carried on there even if that trade is not carried on through a permanent establishment but each of us intend that we will operate in such a manner that none of us will fall within the charge to income tax in the United Kingdom (other than by deduction or withholding) in this respect.

If any of us, other than Aspen U.K. Holdings, Aspen Re and Aspen U.K. Services, were treated as being resident in the United Kingdom for U.K. corporation tax purposes, or if any of us were to be treated as carrying on a trade in the United Kingdom through a permanent establishment, our results of operations could be materially adversely affected.

10% or more of Aspen Holdings' shares may be subject to U.S. income taxation under the
"controlled foreign corporation" ("CFC") rules.

If you are a "10% U.S. Shareholder" of a foreign corporation (defined as a U.S. Person (as defined in "Material Tax Considerations — Taxation of Shareholders — United States Taxation") who owns (directly, indirectly through foreign entities or "constructively" (as defined below)) at least 10% of the total combined voting power of all classes of stock entitled to vote of the foreign corporation), that is a CFC for an uninterrupted period of 30 days or more during a taxable year, and you own shares in the CFC directly or indirectly through foreign entities on the last day of the CFC's taxable year, you must include in your gross income for U.S. federal income tax purposes your pro rata share of the CFC's "subpart F income," even if the subpart F income is not distributed, in which case your investment could be materially adversely affected. A foreign corporation is considered a CFC if "10% U.S. Shareholders" own (directly, indirectly through foreign entities or by attribution by application of the constructive ownership rules of section 958(b) of the Code (i.e., "constructively")) more than 50% of the total combined voting power of all classes of voting stock of that foreign corporation, or the total value of all stock of that foreign corporation. For purposes of taking into account insurance income, a CFC also includes a foreign insurance company in which more than 25% of the total combined voting power of all classes of stock (or more than 25% of the total value of the stock) is owned by 10% U.S. Shareholders on any day during the taxable year of such corporation, if the gross amount of premiums or other consideration for the reinsurance or the issuing of insurance or annuity contracts exceeds 75% of the gross amount of all premiums or other consideration in respect of all risks.

We believe that because of the anticipated dispersion of our share ownership, provisions in our organizational documents that limit voting power (these provisions are described in "Description of Share Capital") and other factors, no U.S. Person who owns shares of Aspen Holdings directly or indirectly through one or more foreign entities should be treated as owning (directly, indirectly through foreign entities, or constructively) 10% or more of the total voting power of all classes of shares of Aspen Holdings or any of its foreign subsidiaries. It is possible, however, that the IRS could challenge the effectiveness of these provisions and that a court could sustain such a challenge. See "Material Tax Considerations — Taxation of Shareholders — United States Taxation — Classification of Aspen Holdings or Its Foreign Subsidiaries as Controlled Foreign Corporations."

U.S. Persons who hold ordinary shares may be subject to U.S. income taxation at ordinary income rates on their proportionate share of our "related party insurance income" ("RPII").

If the RPII (determined on a gross basis) of any foreign Insurance Subsidiary were to equal or exceed 20% of that company's gross insurance income in any taxable year and direct or indirect insureds (and persons related to those insureds) own directly or indirectly through entities 20% or more of the voting power or value of Aspen Holdings, then a U.S. Person who owns any shares of the Company (directly or indirectly through foreign entities) on the last day of the taxable year would be required to include in its income for U.S. federal income tax purposes such person's pro rata share of such company's RPII for the entire taxable year, determined as if such RPII were distributed proportionately only to U.S. Persons at that date regardless of whether such income is distributed, in which case your investment could be materially adversely affected. In addition, any RPII that is includible in the income of a U.S. tax-exempt organization may be treated as unrelated business

32

---

taxable income. The amount of RPII earned by a foreign Insurance Subsidiary (generally, premium and related investment income from the indirect or direct insurance or reinsurance of any direct or indirect U.S. holder of ordinary shares or any person related to such holder) will depend on a number of factors, including the identity of persons directly or indirectly insured or reinsured by the company. We believe that the direct or indirect insureds of the foreign Insurance Subsidiaries (and related persons) did not directly or indirectly own 20% or more of either the voting power or value of our ordinary shares in prior years of operation and we do not expect this to be the case in the foreseeable future. Additionally, we do not expect gross RPII of either foreign Insurance Subsidiary to equal or exceed 20% of its gross insurance income in any taxable year for the foreseeable future, but we cannot be certain that this will be the case because some of the factors which determine the extent of RPII may be beyond our control.

The RPII rules provide that if a U.S. Person disposes of shares in a foreign insurance corporation in which U.S. Persons own 25% or more of the shares (even if the amount of gross RPII is less than 20% of the corporation's gross insurance income and the ownership of its shares by direct or indirect insureds and related persons is less than the 20% threshold), any gain from the disposition will generally be treated as a dividend to the extent of the holder's share of the corporation's undistributed earnings and profits that were accumulated during the period that the holder owned the shares (whether or not such earnings and profits are attributable to RPII). In addition, such a holder will be required to comply with certain reporting requirements, regardless of the amount of shares owned by the holder. These RPII rules should not apply to dispositions of ordinary shares because the Company will not itself be directly engaged in the insurance business. The RPII provisions, however, have never been interpreted by the courts or the Treasury Department in final regulations, and regulations interpreting the RPII provisions of the Code exist only in proposed form. It is not certain whether these regulations will be adopted in their proposed form or what changes or clarifications might ultimately be made thereto or whether any such changes, as well as any interpretation or application of the RPII rules by the IRS, the courts, or otherwise, might have retroactive effect. The Treasury Department has authority to impose, among other things, additional reporting requirements with respect to RPII. Accordingly, the meaning of the RPII provisions and the application thereof to us is uncertain. See "Material Tax Considerations — Taxation of Shareholders — United States Taxation — The RPII CFC Provisions."

U.S. Persons who hold ordinary shares will be subject to adverse tax consequences if we are
considered to be a passive foreign investment company ("PFIC") for U.S. federal income tax purposes.

If we are considered a PFIC for U.S. federal income tax purposes, a U.S. Person who owns any shares of the Company will be subject to adverse tax consequences including subjecting the investor to a greater tax liability than might otherwise apply and subjecting the investor to tax on amounts in advance of when tax would otherwise be imposed, in which case your investment could be materially adversely affected. In addition, if we were considered a PFIC, upon the death of any U.S. individual owning ordinary shares, such individual's heirs or estate would not be entitled to a "step-up" in the basis of the ordinary shares that might otherwise be available under U.S. federal income tax laws. We believe that we are not, have not been, and currently do not expect to become, a PFIC for U.S. federal income tax purposes. We cannot assure you, however, that we will not be deemed a PFIC by the IRS. If we were considered a PFIC, it could have material adverse tax consequences for an investor that is subject to U.S. federal income taxation. There are currently no regulations regarding the application of the PFIC provisions to an insurance company. New regulations or pronouncements interpreting or clarifying these rules may be forthcoming. We cannot predict what impact, if any, such guidance would have on an investor that is subject to U.S. federal income taxation. See "Material Tax Considerations — Taxation of Shareholders — United States Taxation — Passive Foreign Investment Companies."

33

---

U.S. Persons who hold ordinary shares will be subject to adverse tax consequences if we or any of
our foreign subsidiaries are considered to be a foreign personal holding company ("FPHC") for
U.S. federal income tax purposes.

If we were considered an FPHC it could have material adverse tax consequences for our shareholders who are subject to U.S. federal income taxation, including subjecting such shareholders to a greater tax liability than might otherwise apply and subjecting such shareholders to tax on amounts in advance of when tax would otherwise be imposed. In addition, if we were considered an FPHC, upon the death of any U.S. individual owning ordinary shares, such individual's heirs or estate would not be entitled to a "step-up" in the basis of the ordinary shares which might otherwise be available under U.S. federal income tax laws. The Company and/or any of its foreign subsidiaries could be considered to be an FPHC for U.S. federal income tax purposes if more than 50% of our shares could be deemed to be owned by five or fewer individuals who are citizens or residents of the United States, and 60% or more of the Company's income, or that of its foreign subsidiaries, consists of "foreign personal holding company income," as determined for U.S. federal income tax purposes. We believe, based upon information made available to us regarding our existing shareholder base, that neither the Company nor any of its foreign subsidiaries should be considered an FPHC for any prior year of operations or currently. Additionally, we intend to manage our business to minimize the possibility that we will meet the 60% income threshold so that neither the Company nor any of its foreign subsidiaries should be considered an FPHC. However, because of the legal and factual uncertainties regarding the application of the constructive ownership rules, the makeup of our shareholder base, our gross income and other circumstances, we cannot be certain that the Company and/or any of its foreign subsidiaries will not be considered an FPHC. See "Material Tax Considerations — Taxation of Shareholders — United States Taxation — Foreign Personal Holding Companies."

U.S. tax-exempt organizations who own our ordinary shares may recognize unrelated business taxable income.

A U.S. tax-exempt organization may recognize unrelated business taxable income if a portion of the insurance income of either of the foreign Insurance Subsidiaries is allocated to the organization, which generally would be the case if either of the foreign Insurance Subsidiaries is a CFC and the tax-exempt shareholder is a U.S. 10% Shareholder or there is RPII, certain exceptions do not apply and the tax-exempt organization owns any shares of the Company. Although we do not believe that any U.S. Persons should be allocated such insurance income, we cannot be certain that this will be the case. See "Material Tax Considerations — Taxation of Shareholders — United States Taxation — Classification of Aspen Holdings or its Foreign Subsidiaries as Controlled Foreign Corporations" and "Material Tax Considerations — Taxation of Shareholders — United States Taxation — The RPII CFC Provisions." U.S. tax-exempt investors are advised to consult their own tax advisors.

Changes in U.S. federal income tax law could materially adversely affect an investment in our
ordinary shares.

Legislation has been introduced in the U.S. Congress intended to eliminate certain perceived tax advantages of companies (including insurance companies) that have legal domiciles outside the United States but have certain U.S. connections. In this regard, legislation has been introduced that includes a provision which permits the IRS to reallocate or recharacterize items of income, deduction or certain other items related to a reinsurance agreement between related parties to reflect the proper source, character and amount for each item (in contrast to current law, which only refers to source and character). While there are no currently pending legislative proposals which, if enacted, would have a material adverse effect on us or our shareholders, it is possible that broader-based legislative proposals could emerge in the future that could have an adverse impact on us, or our shareholders.

Additionally, the U.S. federal income tax laws and interpretations regarding whether a company is engaged in a trade or business within the United States, or is a PFIC, or whether U.S. Persons would be required to include in their gross income the "subpart F income" or the RPII of a CFC are subject

34

---

to change, possibly on a retroactive basis. There are currently no regulations regarding the application of the PFIC rules to insurance companies and the regulations regarding RPII are still in proposed form. New regulations or pronouncements interpreting or clarifying such rules may be forthcoming. We cannot be certain if, when or in what form such regulations or pronouncements may be provided and whether such guidance will have a retroactive effect.

The impact of Bermuda's letter of commitment to the organization for economic cooperation and
development to eliminate harmful tax practices is uncertain and could adversely affect our tax status in Bermuda.

The Organization for Economic Cooperation and Development (the "OECD"), has published reports and launched a global dialogue among member and non-member countries on measures to limit harmful tax competition. These measures are largely directed at counteracting the effects of tax havens and preferential tax regimes in countries around the world. In the OECD's report dated April 18, 2002 and updated as of June 2004, Bermuda was not listed as a tax haven jurisdiction because it had previously signed a letter committing itself to eliminate harmful tax practices and to embrace international tax standards for transparency, exchange of information and the elimination of any aspects of the regimes for financial and other services that attract business with no substantial domestic activity. We are not able to predict what changes will arise from the commitment or whether such changes will subject us to additional taxes.

35

---

FORWARD-LOOKING STATEMENTS

Some of the statements under "Prospectus Summary," "Risk Factors," "Management's Discussion and Analysis of Financial Condition and Results of Operations," "Business" and elsewhere in this prospectus may include, and the Company may from time to time make other verbal or written, forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act that involve risks and uncertainties, including statements regarding our capital needs, business strategy, expectations and intentions. Statements that use the terms "believe," "do not believe," "anticipate," "expect," "plan," "estimate," "intend" and similar expressions are intended to identify forward-looking statements. These statements reflect our current views with respect to future events and because our business is subject to numerous risks, uncertainties and other factors, our actual results could differ materially from those anticipated in the forward-looking statements, and the differences could be significant. The risks, uncertainties and other factors set forth below and under "Risk Factors" and other cautionary statements made in this prospectus should be read and understood as being applicable to all related forward-looking statements wherever they appear in this prospectus.

All forward-looking statements address matters that involve risks and uncertainties. Accordingly, there are or will be important factors that could cause actual results to differ materially from those indicated in these statements. We believe that these factors include, but are not limited to, those set forth under "Risk Factors" and the following:

•	our short operating history;

•	the impact of acts of terrorism and acts of war;

•	greater frequency or severity of claims and loss activity, including as a result of natural or man-made catastrophic events, than our underwriting, reserving or investment practices have anticipated;

•	the effectiveness of our loss limitation methods;

•	changes in the availability, cost or quality of reinsurance or retrocessional coverage;

•	loss of key personnel;

•	the inability to maintain financial strength or claims-paying ratings by one or more of our subsidiaries;

•	changes in general economic conditions, including inflation, foreign currency exchange rates, interest rates and other factors that could affect our investment portfolio;

•	increased competition on the basis of pricing, capacity, coverage terms or other factors;

•	the effects of terrorist-related insurance legislation and laws;

•	decreased demand for our insurance or reinsurance products and cyclical downturn of the industry;

•	changes in regulations or tax laws applicable to us, our subsidiaries, brokers or customers; and

•	Aspen Holdings or Aspen Bermuda becomes subject to income taxes in the United States or the United Kingdom.

The loss estimates regarding hurricanes Charley, Frances, Ivan and Jeanne and Typhoon Songda, as well as the impact of industry losses on pricing and terms and conditions, could be affected by the following:

•	the total industry losses resulting from these storms;

•	the actual number of the Company's insureds incurring losses from these storms;

•	the limited actual loss reports received from the Company's insureds to date;

36

---

•	the Company's reliance on industry loss estimates and those generated by modelling techniques;

•	the amount and timing of losses actually incurred and reported by insureds to the Company;

•	the preliminary nature of the range of loss estimates to date from the insurance industry;

•	the limited ability of claims personnel of insureds to make inspections and assess claims of losses to date;

•	the inherent uncertainties of establishing estimates and reserves for losses and loss adjustment expenses;

•	the impact of these storms on the Company's reinsurers;

•	the amount and timing of reinsurance recoverables and reimbursements actually received by the Company from its reinsurers; and

•	the overall level of competition, and the related demand and supply dynamics, in the wind exposed property reinsurance lines as contracts come up for renewal.

The foregoing review of important factors should not be construed as exhaustive and should be read in conjunction with the other cautionary statements that are included in this prospectus. We undertake no obligation to publicly update or review any forward-looking statement, whether as a result of new information, future developments or otherwise or disclose any difference between our actual results and those reflected in such statements.

If one or more of these or other risks or uncertainties materialize, or if our underlying assumptions prove to be incorrect, actual results may vary materially from what we projected. Any forward-looking statements you read in this prospectus reflect our current views with respect to future events and are subject to these and other risks, uncertainties and assumptions relating to our operations, results of operations, growth strategy and liquidity. All subsequent written and oral forward-looking statements attributable to us or individuals acting on our behalf are expressly qualified in their entirety by the points made above. You should specifically consider the factors identified in this prospectus which could cause actual results to differ before making an investment decision.

37

---

USE OF PROCEEDS

We will not receive any proceeds from the sale of ordinary shares by the selling shareholder. The selling shareholder will pay any underwriting discounts and commissions and expenses incurred by the selling shareholder for brokerage, accounting or tax services or any other expenses incurred in disposing of the shares. We will bear all other costs, fees and expenses incurred in effecting the registration of the ordinary shares covered by this prospectus, including, without limitation, all registration and filing fees, NYSE listing fees, printing fees, and fees and expenses of our counsel and our accountants as well as the reasonable fees and disbursements of counsel to the selling shareholder.

A portion of the ordinary shares covered by this prospectus are, prior to their resale pursuant to this prospectus, issuable upon exercise of options described herein. Upon any exercise of the Names' Options by payment of cash, we will receive the exercise price of the options. The selling shareholder has delivered a notice to the Company that it will exercise 5,538 Names' Options on a cash basis pursuant to which we will receive aggregate proceeds of approximately £61,527 (approximately $110,250 based on an exchange rate of $1.7919 to £1 on October 12, 2004). We currently expect to use that cash for working capital and general corporate purposes.

PRICE RANGE OF OUR ORDINARY SHARES

Our ordinary shares began trading publicly on December 4, 2003 on the NYSE under the symbol "AHL". Prior to that time, there was no trading market for our ordinary shares. The following table sets forth, for the months, fiscal quarters and periods indicated, the high and low sale prices per ordinary share as reported on the NYSE since our initial public offering on December 4, 2003:

				High				Low
2003
Fourth Quarter (beginning December 4, 2003)				$	25.75			$	23.30
2004
First Quarter					27.22				24.60
Second Quarter					26.00				23.20
Third Quarter					24.95				23.00
Most recent six months
September					24.10				23.00
August					24.31				23.56
July					24.95				23.10
June					25.10				23.20
May					24.20				23.40
April					26.00				23.32

On October 12, 2004, the closing price of our ordinary shares as reported on the NYSE was $23.70. The approximate number of record holders of our ordinary shares as of October 12, 2004 was 86, not including beneficial owners of shares registered in nominee or street name.

38

---

DIVIDEND POLICY

Our board of directors has declared a dividend of $0.03 per ordinary share in each of the first, second and third quarters of 2004 and going forward it intends to authorize the payment of a dividend of $0.03 per ordinary share per fiscal quarter to our shareholders of record. Any determination to pay cash dividends will be at the discretion of our board of directors and will be dependent upon our results of operations and cash flows, our financial position and capital requirements, general business conditions, legal, tax, regulatory and any contractual restrictions on the payment of dividends and any other factors our board of directors deems relevant at the time.

We are a holding company and have no direct operations. Our ability to pay dividends depends, in part, on the ability of our Insurance Subsidiaries to pay dividends to us. The Insurance Subsidiaries are subject to significant regulatory restrictions limiting their ability to declare and pay dividends.

Additionally, we are subject to Bermuda regulatory constraints that will affect our ability to pay dividends on our ordinary shares and make other payments. Under the Companies Act, we may declare or pay a dividend out of distributable reserves only if we have reasonable grounds for believing that we are, and would after the payment be, able to pay our liabilities as they become due and if the realizable value of our assets would thereby not be less than the aggregate of our liabilities and issued share capital and share premium accounts. For a further description of the restrictions on our ability and the ability of our subsidiaries to pay dividends, see "Regulatory Matters — Bermuda Regulation — Minimum Solvency Margin and Restrictions on Dividends and Distributions," "Regulatory Matters — U.K. Regulation — Restrictions on Dividend Payments" and "Regulatory Matters — U.S. Regulation — North Dakota State Dividend Limitations."

Our credit facilities also restrict our ability to pay dividends. See "Management's Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources."

39

---

CAPITALIZATION

The following table sets forth our consolidated capitalization on an actual basis as of June 30, 2004, and as adjusted to give effect to the issuance of 135,321 ordinary shares to the Names' Trustee, of which 128,545 ordinary shares are offered by the Names' Trustee in this offering.

You should read this table in conjunction with "Selected Financial Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the financial statements and related notes that are included elsewhere in this prospectus.

				As of June 30, 2004(1)
				Actual				As Adjusted(2)
				($ in millions)
Debt Outstanding(3)				$	40			$	290
Shareholders' Equity:
Ordinary shares (par value 0.1514458¢)(4)				$	1,092.7			$	1,092.8
Retained earnings					342.4				342.4
Accumulated other comprehensive income, net of taxes(5)					18.4				18.4
Total shareholders' equity					1,453.5				1,453.6
Total Capitalization				$	1,493.5			$	1,743.6

(1)	This table does not give effect to:

	•	the options granted to Wellington for 3,781,120 non-voting shares and to the Names' Trustee for the benefit of the Unaligned Members for an additional 1,710,398 non-voting shares, which options remain exercisable after completion of this offering as further described in "Description of Share Capital — Investor Options" and which non-voting shares will automatically convert into ordinary shares at a one-to-one ratio upon issuance;

	•	3,884,030 ordinary shares that may be issued pursuant to options that have been granted under our share incentive plan at a weighted average exercise price of $16.20 per share and 37,665 restricted share units granted to our employees; and

	•	1,802,885 ordinary shares available for future issuance under our share incentive plan.

(2)	The "As Adjusted" columns:

	•	reflects 135,321 ordinary shares issued pursuant to the cash and cashless exercise of options held by the Names' Trustee on behalf of the Unaligned Members for an estimate aggregate subscription price of approximately £61,527 (approximately $110,250 based on an exchange rate of $1.7919 to £1 on October 12, 2004); and

	•	reflects the offering by the Company of $250 million in aggregate principal amount of 6.00% Senior Notes due 2014.

(3)

On August 16, 2004, we completed our offering of $250 million in aggregate principal amount of 6.00% Senior Notes due 2014. On October 15, 2003, we made a drawdown of $90 million on our three-year revolving credit facility. We have previously repaid $50 million and intend to repay the $40 million in principal amount of outstanding borrowing under the credit facility at the end of the current interest period.

(4)	As of June 30, 2004, we had 69,174,303 ordinary shares outstanding. No non-voting shares or preference shares were outstanding as of June 30, 2004. As adjusted to give effect to the issuance of the ordinary shares upon the exercise of the Names' Options, a portion of which are sold in this offering we will have 69,309,624 ordinary shares outstanding.

(5)	Includes unrealized gains on investments and unrealized gains on foreign currency.

40

---

DILUTION

As of June 30, 2004, our net tangible book value was $1,446.9 million, or $20.92 per ordinary share, assuming 69,174,303 ordinary shares outstanding. As used below, our net tangible book value per ordinary share represents shareholders' equity, minus the balance for intangible assets, divided by the number of ordinary shares outstanding. After giving effect to the issuance of 135,321 of our ordinary shares upon the exercise of 856,218 options held by the Names' Trustee, 5,538 on a cash basis and 850,680 on a cashless basis and after the application of the estimated proceeds from the issuance of the ordinary shares to the Names' Trustee, our net tangible book value as of June 30, 2004 would have been approximately $1,447 million, or $20.88 per ordinary share. This amount represents an immediate decrease of $0.04 per ordinary share to the existing shareholders and an immediate dilution of $2.62 per ordinary share issued to the new investors purchasing shares offered hereby, based on an assumed offering price of $23.50 per ordinary share. Dilution in net tangible book value per ordinary share represents the difference between the assumed amount per ordinary share and the net tangible book value per ordinary share. The following table illustrates this per share dilution:

Assumed public offering price per ordinary share				$	23.50
Net tangible book value per ordinary share before the offering					20.92
Decrease attributable to the offering					0.04
Net tangible book value per ordinary share after the offering					20.88
Dilution per ordinary share to new investors				$	2.62

41

---

SELECTED CONSOLIDATED FINANCIAL DATA

The following table sets forth our selected historical financial information for the periods ended and as of the dates indicated. The summary income statement data for the period from our inception at May 23, 2002 through December 31, 2002 and for the twelve months ended December 31, 2003 and the balance sheet data as of December 31, 2003 and 2002 are derived from our audited consolidated financial statements included elsewhere in this prospectus, which have been prepared in accordance with U.S. GAAP and have been audited by KPMG Audit Plc, our independent auditors. The summary income statement data for the six months ended June 30, 2004 and June 30, 2003 and the summary balance sheet data as at June 30, 2004 are derived from our unaudited condensed consolidated financial statements included elsewhere in this prospectus. The unaudited condensed consolidated financial statements have been prepared on the same basis as our audited consolidated financial statements and in our opinion, include all adjustments, consisting only of normal recurring adjustments which we consider necessary for a fair presentation of our results of operations and financial position for these periods. These historical results are not necessarily indicative of results to be expected from any future period, and the results presented below are not necessarily indicative of our full year performance. Due to our limited operating history, the ratios presented may not be indicative of our future performance. You should read the following selected consolidated financial information along with the information contained in this prospectus, including "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the audited consolidated financial statements, unaudited condensed consolidated financial statements and related notes included elsewhere in this prospectus.

				Six Months Ended June 30,								Periods Ended December 31,
				2004				2003				2003				2002 (1)
				($ in millions, except per share amounts and percentages)
Summary Income Statement Data
Gross premiums written				$	1,020.6			$	830.0			$	1,306.8			$	374.8
Net premiums written					873.0				666.0				1,092.8				312.6
Net premiums earned					632.8				332.3				812.3				120.3
Loss and loss adjustment expenses					(263.5	)			(165.9	)			(428.4	)			(76.9	)
Policy acquisition and general and administrative expenses					(168.4	)			(85.6	)			(205.6	)			(29.8	)
Net Investment Income					26.9				10.7				29.6				8.5
Net Income					165.9				65.1				152.1				28.6
Basic earnings per share					2.40				1.14				2.63				0.89
Fully diluted earnings per share					2.31				1.14				2.56				0.89
Basic weighted average shares outstanding					69.1				56.9