DR Darwin Professional Underwriters

A.M. Best Co. has placed the financial strength rating (FSR) of A- (Excellent) and issuer credit ratings (ICR) of �a-� of Darwin Group (Darwin) (Wilmington, DE) and its members under review with positive implications. Concurrently, the FSR of A- (Excellent) and ICR of �a-� of Vantapro Specialty Insurance Company (Vantapro) (Chicago, IL) remain under review, and the implications have been revised to developing from negative. (See below for a detailed listing of the companies and ratings.) These rating actions follow the recent announcement that Allied World Assurance Company Holdings, Ltd (Allied World Holdings) (Bermuda) [NYSE: AWH] has entered into a definitive agreement to acquire Darwin Professional Underwriters, Inc. (DPUI) (Wilmington, DE) [NYSE: DR]. A.M. Best expects the ICR of �bbb-� of DPUI to be withdrawn upon the completion of its acquisition by Allied World Holdings. The under review status also reflects the pending implementation of a substantial quota share reinsurance agreement between Darwin and Allied World Assurance Company, Ltd (Bermuda) (Allied World), a subsidiary of Allied World Holdings. Vantapro was originally placed under review pending the implementation of a substantial quota share reinsurance agreement between Vantapro and its immediate parent, Darwin National Assurance Company (Delaware). Vantapro also is expected to be party to the quota share reinsurance agreement with Allied World. The ratings will remain under review pending the completion of the transaction, which is subject to the satisfaction of certain closing conditions and is expected to close during fourth quarter 2008, and once the quota share reinsurance agreements have been approved and implemented. At that time, A.M. Best will likely upgrade and remove the ratings from under review based upon the explicit support provided by Allied World through the quota share agreement. The FSR of A- (Excellent) and ICRs of �a-� have been placed under review with positive implications for Darwin Group and its following members: Darwin National Assurance Company Darwin Select Insurance Company The FSR of A- (Excellent) and ICR of �a-� remain under review and the implications have been revised to developing from negative for Vantapro Specialty Insurance Company. 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.