SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 20549
                                 ---------------

                                    FORM 8-K

                                 CURRENT REPORT
                     PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934



Date of Report (Date of earliest event reported)         December 19, 1999
                                                --------------------------------

                               Trenwick Group Inc.
- --------------------------------------------------------------------------------
             (Exact Name of Registrant as Specified in its Charter)



Delaware                            0-14737                          06-1152790
- --------------------------------------------------------------------------------
State or Other Jurisdiction       (Commission                     (IRS Employer
of Incorporation)                  File Number)                   Identification
No.)



One Canterbury Green, Stamford, Connecticut                              06901
- ---------------------------------------------                  -----------------
 (Address of Principal Executive Offices)                            (Zip Code)



Registrant's telephone number, including area code         (203) 353-5500
                                                   -----------------------------


          (Former Name or Former Address, if Changed Since Last Report)






Item 5. - Other Events

         Trenwick Group Inc., a Delaware corporation ("Trenwick"),  entered into
a  definitive  Agreement,  Scheme of  Arrangement,  Plan of  Merger  and Plan of
Reorganization,  dated  as of  December  19,  1999  (the  "Business  Combination
Agreement")  with LaSalle Re Holdings  Limited,  a Bermuda company  ("LaSalle"),
LaSalle Re Limited, a Bermuda company ("LaSalle Re"),  Trenwick Group (Delaware)
Inc.  and  Gowin  Holdings   International   Limited,   pursuant  to  which  the
stockholders  of Trenwick,  the common  stockholders of LaSalle and the minority
shareholders  of LaSalle Re will each  exchange  their  shares on a  one-for-one
basis for shares in a newly formed Bermuda company (the "Business Combination").
See the full text of the Business Combination  Agreement which is filed herewith
as Exhibit 2.1 and which is incorporated by reference herein.

         In connection  with the Business  Combination  Agreement,  Trenwick and
LaSalle  have  granted to each other  options to  purchase  up to 19.9% of their
outstanding  shares  pursuant  to  Stock  Option  Agreements,  each  dated as of
December 19, 1999.  See the full text of the Stock Option  Agreements  which are
filed herewith as Exhibits 99.1 and 99.2 and which are incorporated by reference
herein.

         Certain  shareholders  of LaSalle  and  LaSalle Re have  agreed to vote
their  shareholdings  in  favor  of  the  Business  Combination  pursuant  to  a
Shareholders Agreement,  dated as of December 19, 1999. See the full text of the
Shareholders  Agreement  which is filed  herewith  as Exhibit  99.3 and which is
incorporated by reference herein.

         On December 19, 1999, Trenwick and LaSalle issued a joint press release
announcing the Business Combination, which is filed herewith as Exhibit 99.4 and
which is incorporated by reference herein.

Item 7. Financial Statements and Exhibits

(c)      Exhibits

2.1      Agreement,   Scheme  of  Arrangement,   Plan  of  Merger  and  Plan  of
         Reorganization,  dated as of December 19, 1999, by and among LaSalle Re
         Holdings  Limited,  LaSalle Re Limited,  Trenwick Group Inc.,  Trenwick
         Group (Delaware) Inc. and Gowin Holdings International Limited.

99.1     Stock Option Agreement, dated as of December 19, 1999, between Trenwick
         Group Inc. and LaSalle Re Holdings  Limited  (option granted to LaSalle
         Re Holdings Limited).

99.2     Stock Option Agreement, dated as of December 19, 1999, between Trenwick
         Group Inc. and LaSalle Re Holdings Limited (option granted to Trenwick
         Group Inc.).

99.3     Shareholders  Agreement,  dated as of December 19,  1999,  by and among
         Trenwick Group Inc.,  Combined  Insurance Company of America,  Virginia
         Surety Company,  Inc., Aon Risk Consultants (Bermuda) Ltd., Continental
         Casualty Company and CNA (Bermuda) Services Limited.

99.4     Press release of Trenwick Group Inc. and LaSalle Re Holdings Limited
         issued December 19, 1999.



                                    SIGNATURE

         Pursuant to the  Requirements  of the Securities  Exchange Act of 1934,
the  registrant  has duly  caused  this report to be signed on its behalf by the
undersigned hereunto duly authorized.

                                            TRENWICK GROUP INC.


                                            By:   /s/ James F. Billett, Jr.
                                                  ----------------------------
                                                  James F. Billett, Jr.
                                                  Chairman, President and
                                                  Chief Executive Officer




Dated:  December 22, 1999




                                  EXHIBIT INDEX



Exhibit                    Description of Exhibit

2.1      Agreement,   Scheme  of  Arrangement,   Plan  of  Merger  and  Plan  of
         Reorganization, dated as of December 19, 1999, by  and among LaSalle Re
         Holdings  Limited,  LaSalle Re Limited,  Trenwick Group Inc.,  Trenwick
         Group (Delaware) Inc. and Gowin Holdings International Limited.

99.1     Stock Option Agreement, dated as of December 19, 1999, between Trenwick
         Group Inc. and LaSalle Re Holdings  Limited  (option granted to LaSalle
         Re Holdings Limited).

99.2     Stock Option Agreement, dated as of December 19, 1999, between Trenwick
         Group Inc. and LaSalle Re Holdings Limited (option granted to  Trenwick
         Group Inc.).

99.3     Shareholders  Agreement,  dated as of December 19,  1999,  by and among
         Trenwick Group Inc.,  Combined  Insurance Company of America,  Virginia
         Surety Company,  Inc., Aon Risk Consultants (Bermuda) Ltd., Continental
         Casualty Company and CNA (Bermuda) Services Limited.

99.4     Press  release  of Trenwick  Group Inc. and LaSalle Re Holdings Limited
         issued December 19, 1999.