LaSalle Re Holdings Limited
                               Trenwick Group Ltd.
                                25 Church Street
                                 Hamilton HM 12
                                     Bermuda

                                                  September 27, 2000



Mr.  David  R. Whiting
Member of Senior Management
European Reinsurance Company of Zurich
8 Par-la-Ville Road
Hamilton HM 08
Bermuda


Re: Catastrophe Equity Securities Issuance Option Agreement entered into as of
    July 1, 1999 (the "Agreement")

Dear David:

Subject  to  the  second  and  third  sentences  of  this  paragraph,   European
Reinsurance  Company of Zurich ("ERZ"),  as holder of a Majority Option Interest
as defined in the  Agreement,  approves the Change in Control (as defined in the
Agreement)  resulting from the consummation of the transactions  contemplated by
the  Amended  and  Restated  Agreement,  Schemes  of  Arrangement  and  Plan  of
Reorganization,  dated as of March 20, 2000 and amended as of June 28, 2000,  by
and among LaSalle Re Holdings  Limited,  a company  organized  under the laws of
Bermuda ("LaSalle Holdings"),  LaSalle Re Limited, a company organized under the
laws of Bermuda and a majority-owned  subsidiary of LaSalle  Holdings  ("LaSalle
Re"),  Trenwick  Group  Inc.,  a Delaware  corporation  ("Trenwick"),  and Gowin
Holdings  International  Limited,  a company organized under the laws of Bermuda
which has changed its name to Trenwick Group Ltd. ("New Holdings"),  whereby (i)
holders of common shares of LaSalle Holdings ("LaSalle Common Shares"),  holders
of  exchangeable  non-voting  common  shares of LaSalle Re and holders of common
stock of Trenwick  will become  shareholders  of New  Holdings  and (ii) LaSalle
Holdings,  LaSalle Re and the  current  subsidiaries  of  Trenwick  will  become
subsidiaries  of New  Holdings  (the  "Business  Combination"),  which  Business
Combination is scheduled to close on or about September 27, 2000. As a result of
this approval,  in accordance  with Section 6.8 of the Agreement,  the Agreement
shall remain in full force and effect;  provided,  however,  that the  Agreement
shall only remain in effect for a  transition  period  ending at 11:59:59  p.m.,
Bermuda Time, on December 31, 2000 (the "Transition Period"), subject to payment
to the Option Writers (as defined in the Agreement) of a pro rata portion of the
Option Fee (as defined in the Agreement)  that is due on October 1, 2000 for the
period from October 1, 2000 through  December 31, 2000, ERZ and LaSalle Holdings
agree that immediately  following the end of the Transition  Period, the fact of
the Business  Combination  having been consummated  shall constitute a Change in
Control  for  purposes of Section 6.8 of the  Agreement.

For the avoidance of doubt,  during the  Transition  Period,  the  definition of
"Company  Subsidiaries"  in the  Agreement  shall  remain  unchanged  and  shall
continue to refer  exclusively to LaSalle Re, LaSalle Re Corporate Capital Ltd.,
a company  formed  under the laws of Bermuda,  and such other direct or indirect
subsidiaries  of LaSalle  Holdings as may be agreed in writing  between  LaSalle
Holdings and the Option Writers.

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<PAGE>


Inasmuch as the  Agreement  provides  for the  purchase  by the Option  Writers,
subject to the terms and conditions  thereof,  of Series B Preferred Shares, par
value  $1.00 per share,  of LaSalle  Holdings  ("Preferred  Shares"),  which are
convertible  by their terms into LaSalle  Common  Shares,  New  Holdings  hereby
assumes,  subject to and  concurrently  with the  consummation  of the  Business
Combination,  the obligation to deliver to each holder of Preferred  Shares,  in
the  event of any  conversion  thereof,  upon the  basis  and upon the terms and
conditions specified in Section 6 of the Certificate of Designation, Preferences
and Rights of the Preferred Shares (the  "Certificate"),  in lieu of the LaSalle
Common  Shares  that  would have been  delivered  upon such  conversion  had the
Business  Combination not been consummated,  common shares of New Holdings ("New
Holdings  Common  Shares"),  provided that all references in the  Certificate to
"Common  Shares"  shall be deemed to refer to New Holdings  Common Shares rather
than to LaSalle Common Shares.

Inasmuch  as  LaSalle  Holdings  and the  Option  Writers  have  entered  into a
Registration  Rights  Agreement,  dated as of July 1,  1997  (the  "Registration
Rights Agreement"),  which grants the Option Writers certain registration rights
with respect to LaSalle  Common  Shares  issued  pursuant to the  conversion  of
Preferred Shares, New Holdings hereby assumes,  subject to and concurrently with
the  consummation  of the  Business  Combination,  the  obligations  of  LaSalle
Holdings pursuant to the Registration  Rights Agreement;  provided that (a) such
obligations  shall  apply to the New  Holdings  Common  Shares  rather  than the
LaSalle  Common Shares;  and (b) the New Holdings  Common Shares rather than the
LaSalle  Common  Shares  shall  constitute  Conversion  Shares  and  Registrable
Securities for the purposes of the Registration Rights Agreement.

Please  confirm  the above  agreement  by signing  and  returning  the  enclosed
duplicate  original  of this  letter by both fax and  courier  at your  earliest
convenience,  but in no case later than September 26, 2000. Your  cooperation is
appreciated.

Sincerely,

LASALLE RE HOLDINGS LIMITED                         TRENWICK GROUP LTD.


By:   /s/ Clare Moran                               By: /s/ John V. Del Col
    -----------------------                             -----------------------
Name:    Clare Moran                                Name:  John V. Del Col
Title:   SVP - Finance                              Title: SVP, General Counsel
                                                           and Secretary


Accepted and Agreed:

EUROPEAN REINSURANCE COMPANY OF ZURICH


By:   /s/ David R. Whiting                          By: /s/  Tim Courtis
   -------------------------                           -------------------------
Name:    David R. Whiting                           Name:  Tim Courtis
Title:   Member of Senior Management                Title: Member of Senior
                                                           Management







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