AHL Aspen Insurance Holdings Limited Ordinary Shares

A.M. Best Co. has upgraded the financial strength rating to A (Excellent) from A- (Excellent) and the issuer credit rating (ICR) to �a� from �a-� of Aspen Insurance Limited (AIL) (Bermuda). The outlook for both ratings is stable. The rating upgrades reflect a sustainable improvement in AIL�s stand alone risk-adjusted capitalisation, which is likely to be supported by strong retained earnings of above USD 150 million in both 2007 and 2008. In addition, Aspen has continued to balance the spread of business between its two main operating entities, AIL and its sister company, Aspen Insurance UK Limited (AIUK), through the use of intra-group quota share arrangements. This even distribution of risk, AIL�s excellent risk-adjusted capitalisation and excellent financial strength of the consolidated group has led A.M. Best to harmonise the ratings of both entities. (For details on AIUK and its ultimate parent, Aspen Insurance Holdings Ltd. (Aspen) (Bermuda) [NYSE: AHL], please refer to A.M. Best�s press release dated December 7, 2007.) A.M. Best believes that AIL is likely to continue to produce excellent earnings in 2007, benefiting from profitable underwriting, strong rate adequacy in the property catastrophe market (despite weakening) and improved investment returns. A stable combined ratio in the region of 80% is likely, supported by another benign U.S. hurricane season. A.M. Best believes AIL is likely to achieve strong, albeit somewhat weaker performance in 2008 (subject to catastrophe experience), owing to the softening rating environment across all AIL�s main lines of business. In A.M. Best�s opinion, AIL benefits from the strength of the Aspen brand with a significant proportion of its income emanating from intra-group cessions. Overall, AIL has a well diversified book of property and casualty reinsurance (in particular, reinsurance of AIUK) and specialty insurance and reinsurance business (including its significant structured risk account). For Best�s Ratings, an overview of the rating process and rating methodologies, please visit www.ambest.com/ratings. Founded in 1899, A.M. Best Company is a global full-service credit rating organization dedicated to serving the financial and health care service industries, including insurance companies, banks, hospitals and health care system providers. For more information, visit www.ambest.com.