Transaction Creates Premier Reinsurance Franchise with Global Reach, Diverse Product Capability and World Class Colleagues to Serve Clients' Evolving Needs

Aon Corporation (NYSE: AOC) and Benfield Group Limited (LSE: BFD) announced today that the boards of directors of both companies have unanimously approved a definitive agreement under which Aon will acquire Benfield for 3.50 pounds Sterling (US$6.55) per share in cash and assume 91 million pounds (US$170 million) of Benfield net debt, representing an enterprise value of approximately 935 million pounds (US$1.75 billion) on a fully diluted basis. The consideration represents a 29 percent premium to Benfield's closing stock price on August 21, 2008, the last trading day prior to the announcement of the agreement.

Benfield is a leading independent reinsurance intermediary in terms of reputation and standing. The Benfield business is renowned in the industry for its excellent client service, leading analytics capability and record of innovation. Aon believes that, as part of Aon Re Global, Benfield can continue to build upon these strengths, creating an unparalleled reinsurance franchise with global reach, diverse product capability and world class colleagues to effectively serve clients' evolving needs. Following the close of the transaction, Aon intends to integrate the Benfield business with its existing reinsurance operations (Aon Re Global) and operate the division globally under the newly created Aon Benfield Re brand.

"This agreement reflects our ongoing efforts to ensure that Aon's colleagues, capabilities and technology remain at the forefront of our industry and that we provide the best value for our clients," said Greg Case, president and chief executive officer of Aon Corporation. "Over the past several years, we have made significant progress in strengthening Aon's operational platform and global network, becoming a more client-focused organization with a broader portfolio of innovative products and services. With Aon Benfield Re, we will build on this progress to further enhance organic growth, expand margins, and drive shareholder value."

Mr. Case continued, "Aon and Benfield share a common focus on excellence in client service, and both recognize the importance of being the destination of choice for the best talent in our industry. The strong cultural fit between our firms will enable us to quickly realize the benefits of this transaction, and the value added for our clients and shareholders, in a seamless fashion following the close of our transaction."

Grahame Chilton, chief executive officer of Benfield, commented, "We are excited by this unique opportunity to create a powerful global franchise capable of expanding and redefining innovative reinsurance and capital market solutions. At the same time, the Benfield board believes that the offer provides Benfield's shareholders with fair and certain value. We look forward to joining the Aon team and working with them as Aon Benfield Re to expand our joint expertise and local reach to customers around the world."

"I have significant respect and admiration for the Benfield organization," noted Michael O'Halleran, executive chairman of Aon Re Global. "I look forward to working with Grahame, Andrew and our colleagues and team members as we combine the strengths of our two organizations into the leading reinsurance and capital management advisor in the world."

Andrew Appel, chief executive officer of Aon Re Global, added, "The combination of our two firms will create an unparalleled set of capabilities to deliver distinctive client value, drive innovation in analytics and capital management, and enhance the value proposition for colleagues and team members in both businesses."

Advisors

Credit Suisse acted as financial advisor to Aon, and Clifford Chance LLP is serving as legal counsel. Merrill Lynch acted as financial advisor to Benfield, and Debevoise & Plimpton LLP is serving as legal counsel.

About Benfield

Benfield is the world's leading specialist reinsurance and risk intermediary. Its customers include many of the world's major insurance and reinsurance companies as well as government entities and global corporations. Benfield operates from more than 50 locations worldwide. Benfield is listed on the London Stock Exchange under the ticker symbol BFD. For more information on Benfield, log onto http://www.benfieldgroup.com.

About Aon

Aon Corporation is the leading global provider of risk management services, insurance and reinsurance brokerage, human capital and management consulting. Through its 36,000 colleagues worldwide, Aon readily delivers distinctive client value via innovative and effective risk management and workforce productivity solutions. Our industry-leading global resources, technical expertise and industry knowledge are delivered locally through more than 500 offices in more than 120 countries. Aon was named the world's best broker by Euromoney magazine's 2008 Insurance Survey. In 2008, Aon ranked highest on the Business Insurance ranking of the world's largest insurance brokers based on commercial retail, wholesale, reinsurance and personal lines brokerage revenues. Aon also was ranked by A.M. Best as the number one global insurance brokerage in 2007 and 2008 based on brokerage revenues, and voted best insurance intermediary, best reinsurance intermediary, and best employee benefits consulting firm in 2007 and 2008 by the readers of Business Insurance. For more information on Aon, log onto http://www.aon.com.