Exhibit 99.1

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

     [LOGO]

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 COMMENCES ARBITRATION AGAINST SWISS RE

Hamilton, Bermuda - July 1, 2002 -- Trenwick Group Ltd. ("Trenwick") today
commenced an arbitration proceeding seeking $55,000,000 (US) in damages and
other relief against European Reinsurance Company of Zurich, a subsidiary of
Swiss Reinsurance Company. The claims arise out of European Re's failure to meet
its obligations under a Catastrophe Equity Securities Issuance Option Agreement
with Trenwick. The agreement entitles Trenwick to put to European Re 550,000
convertible perpetual preferred shares at a purchase price of $100 per share.

James F. Billett, Jr., Chairman, President and Chief Executive Officer of
Trenwick, stated, "The unfortunate unwillingness of Swiss Re to honor its clear
cut obligations under the Catastrophe Equity Securities Issuance Option
Agreement forces us to demand arbitration. While no dispute resolution mechanism
is certain, we are confident that the facts support our position and believe we
will ultimately prevail."

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.

Each of Trenwick's operating insurance company subsidiaries is rated "A-"
(Excellent) by A.M. Best Company and is assigned an A- financial strength rating
by Standard & Poor's. All of Chartwell Managing Agents Limited's syndicates
underwrite under the ratings of Lloyd's, which is rated "A-" (Excellent) by A.M.
Best Company and has an A financial strength rating from Standard & Poor's.

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.