Trenwick Group Ltd.            LOM Building           Tel  441.292.4985
                                        27 Reid Street         Fax 441.292.4878
                                        Hamilton HM 11
                                        Bermuda

         [LOGO] TRENWICK

         NYSE Symbol: TWK

         Contact: Alan L. Hunte, Executive Vice President and Chief Financial
                  Officer - 441.292.4985

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         For Immediate Release
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             TRENWICK ANNOUNCES AGREEMENT WITH SWISS RE TO PURCHASE
                           TRENWICK PREFERRED SHARES

Hamilton, Bermuda - September 6, 2002 -- Trenwick Group Ltd. ("Trenwick") today
announced that European Reinsurance Company of Zurich, a subsidiary of Swiss
Reinsurance Company, purchased 550,000 of Trenwick's Series B Cumulative
Convertible Perpetual Preferred Shares with a liquidation preference of $100 per
share for an aggregate purchase price of $40 million. The purchase was made
pursuant to a Second Amended and Restated Catastrophe Equity Securities Issuance
Option Agreement between European Re and Trenwick. Concurrently with the
purchase of the preferred shares Trenwick and European Re agreed to terminate
the pending arbitration proceedings, increase the dividend rate applicable to
the preferred shares by 2.0% and reduce the restrictions on European Re's
ability to transfer the preferred shares from three years to six months. The
preferred shares are convertible after five years into Trenwick's common shares
at the higher of Trenwick's book value or common share market value at the time
of conversion.

W. Marston Becker, Acting Chairman and Acting Chief Executive Officer of
Trenwick, stated, "We are pleased to conclude the exercise of the Catastrophe
Option Agreement in a manner satisfactory to both Swiss Re and us."

Background Information

Trenwick is a Bermuda-based specialty insurance and reinsurance underwriting
organization with three principal businesses operating through its subsidiaries



located in the United States, the United Kingdom and Bermuda. Trenwick's
reinsurance business provides treaty reinsurance to insurers of property and
casualty risks from offices in the United States and Bermuda. Trenwick's
international operations underwrite specialty insurance as well as treaty and
facultative reinsurance on a worldwide basis through its London insurer and at
Lloyd's. Trenwick's U.S. specialty program insurance business underwrites U.S.
property and casualty insurance through specialty program administrators.

Safe Harbor for Forward-Looking Statements

Certain statements made in this press release that are not based on current or
historical fact are forward-looking in nature including, without limitation,
statements containing words "believes," "anticipates," "plans," "projects,"
"intends," "expects," "estimates," "predicts," and words of similar import. Such
forward-looking statements, including in particular Trenwick's forecast of
future earnings, involve known and unknown risks, assumptions, uncertainties,
and other factors that may cause actual results, performance, or achievements of
Trenwick or its industry to differ materially from any future results,
performance, or achievements expressed or implied by such forward-looking
statements.

Trenwick has identified certain risk factors which could cause actual plans or
results to differ substantially from those included in any forward-looking
statements. These risk factors are discussed in Trenwick's Securities and
Exchange Commission filings, including but not limited to its most recent Form
10-K, Form 10-Q and Form 8-K filed with the Securities and Exchange Commission,
and such discussions regarding risk factors are hereby incorporated by reference
into this press release. Copies of such Securities and Exchange Commission
filings are available from Trenwick or directly from the Securities and Exchange
Commission.