UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549



                                   FORM 12b-25
                           NOTIFICATION OF LATE FILING


     [ ] Form 10-K [ ] Form 20-F [X] Form 11-K [ ] Form 10-Q [ ] Form N-SAR

                       For Period Ended December 31, 1999

                     [ ] Transition Report on Form 10-K
                     [ ] Transition Report on Form 20-F
                     [ ] Transition Report on Form 11-K
                     [ ] Transition Report on Form 10-Q
                     [ ] Transition Report on Form N-SAR

                   For Transition Period Ended: ______________


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    NOTHING IN THIS FORM SHALL BE CONSTRUED TO IMPLY THAT THE COMMISSION HAS
                   VERIFIED ANY INFORMATION CONTAINED HEREIN.
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If the notification relates to a portion of the filing checked above, identify
the Item(s) to which the notification relates:  _________________________



PART 1 - REGISTRANT INFORMATION



                                                 
Full Name of Registrant:                             WHITE MOUNTAINS INSURANCE GROUP, LTD.
Address of Principal Executive Office:               80 South Main Street
                                                     Hanover, NH 03755

Full Title of Plan:                                  FOLKSAMERICA HOLDING COMPANY
                                                     401(k) SAVINGS AND INVESTMENT PLAN

Address of Plan:                                     One Liberty Plaza, 19th Floor
                                                     New York, NY 10006











PART II - RULES 12B-25(b) AND (c)

If the subject report could not be filed without unreasonable effort or expense
and the registrant seeks relief pursuant to Rule 12b-25(b), the following should
be completed (Check box if appropriate.)

     [X]   (a)  The reasons described in reasonable detail in Part III of
                this form could not be eliminated without unreasonable effort or
                expense.

     [X]   (b)  The subject annual report, semi-annual report, transition
                report on Form 10-K, 20-F, 11-K, 10-Q, N-SAR, or portion thereof
                will be filed on or before the fifteenth calendar day following
                the prescribed due date; or the subject quarterly report or
                transition report on Form 10-Q, or portion thereof will be filed
                on or before the fifth calendar day following the prescribed due
                date; and

     [ ]   (c)  The accountant's statement or other exhibit required by
                Rule 12b-25(c) has been attached if applicable.


PART III - NARRATIVE

STATE BELOW IN REASONABLE DETAIL THE REASONS WHY THE FORM 10-K, 20-F, 11-K,
10-Q, N-SAR, OR THE TRANSITION REPORT OR PORTION THEREOF, COULD NOT BE FILED
WITHIN THE PRESCRIBED TIME PERIOD.

The Registrant requires additional time to gather the information necessary to
prepare a complete and accurate filing.


PART IV - OTHER INFORMATION

(1) Name and telephone number of person to contact in regard to this
notification:

            Michael S. Paquette, Senior Vice President and Controller
                                 (603) 640-2205

(2)  Have all periodic reports required under Section 13 or 15(d) of the
     Securities Exchange Act of 1934 or Section 30 of the Investment Company Act
     of 1940 during the preceding 12 months or for such shorter period that the
     registrant was required to file such report(s) been filed. If answer is no,
     identify report(s). [X] Yes [ ] No

(3)  Is it anticipated that any significant change in the results of operations
     from the corresponding period for the last fiscal year will be reflected by
     the earnings statement to be included in the subject report or portion
     thereof? [ ] Yes [X] No

     If so, attach an explanation of the anticipated change, both narratively
     and quantitatively, and, if appropriate, state the reasons why a reasonable
     estimate of the results cannot be made.













                      WHITE MOUNTAINS INSURANCE GROUP, LTD.
                      -------------------------------------
                (Name of registrant as specified in its charter)

(on behalf of the Folksamerica Holding Company 401(k) Savings and Investment
Plan) has caused this notification to be signed on its behalf by the undersigned
persons hereunto duly authorized.

Date:   June 23, 2000

By: /s/ MICHAEL S. PAQUETTE                By: /s/ MICHAEL E. TYBURSKI
    -------------------------------           -------------------------------
Senior Vice President and Controller               Member
White Mountains Insurance Group, Ltd.              Plan Investment Committee