Exhibit 99.1 Willis Group Announces Exercise of Over-Allotment of 3,000,000 Shares in Secondary Offering NEW YORK--(BUSINESS WIRE)--March 18, 2004--Willis Group Holdings Limited (NYSE: WSH), the global insurance broker, announced today that the underwriters for the company's recently completed secondary offering have exercised in full their over-allotment option to purchase an additional 3,000,000 shares of common stock, resulting in an aggregate of 23,000,000 shares being sold in the secondary offering. Profit Sharing (Overseas) and Fisher Capital Corp. L.L.C. sold the additional shares. Upon completion of the over-allotment, Profit Sharing (Overseas) will own approximately 5.5% of the outstanding shares of Willis. Citigroup, Credit Suisse First Boston and Banc of America Securities LLC served as joint book-running managers of the offering. A final prospectus relating to the common stock offering may be obtained by contacting: Citigroup Prospectus Department Brooklyn Army Terminal 140 58th Street, 5th Floor Brooklyn, NY 11220 718-765-6732 Credit Suisse First Boston Prospectus Department One Madison Avenue New York, NY 10010 212-325-2580 Banc of America Securities LLC Prospectus Department 100 West 33rd Street New York, NY 10001 646-733-4166 Willis Group Holdings is a leading global insurance broker, developing and delivering professional insurance, reinsurance, risk management, financial and human resource consulting and actuarial services to corporations, public entities and institutions around the world. With over 300 offices in more than 74 countries, its global team of 13,000 employees serves over 50,000 clients in 160 countries. Willis has particular expertise in serving the needs of clients in such major industries as construction, aerospace, marine and energy. In June 2001 the Group returned to public ownership and is listed on the New York Stock Exchange. This announcement shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state. The offering of these securities is made only by means of a prospectus. CONTACT: Willis Group Holdings Limited Investors: Kerry K. Calaiaro, 212-837-0880 calaiaro_ke@willis.com or Media: Nicholas Jones, +1 44 20 7488-8190 jonesnr@willis.com or Dan Prince, 212-837-0806 prince_da@willis.com