SCHEDULE 13D

                    Under the Securities Exchange Act of 1934
                                (Final Amendment)


                          San Juan Basin Royalty Trust
                          ----------------------------
                                (Name of Issuer)

                          Units of Beneficial Interest
                          ----------------------------
                         (Title of Class of Securities)

                                    798241105
                                 --------------
                                 (CUSIP Number)

                               Michael S. Paquette
                            Senior Vice President and
                                   Controller
                      White Mountains Insurance Group, Inc.
               (formerly Fund American Enterprises Holdings, Inc.)
                              80 South Main Street
                                Hanover, NH 03755
                                 (603) 640-2205
                                 --------------

            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)

                                 August 19, 1999
             -------------------------------------------------------
             (Date of Event which Requires Filing of this Statement)

         If the filing person has previously filed a statement on Schedule 13G
to report the acquisition which is the subject of this Schedule 13D, and is
filing this schedule because of Rule 13d-1(b)(3) or (4), check the following box
 .

         Check the following box if a fee is being paid with this statement . (A
fee is not required only if the reporting person: (1) has a previous statement
on file reporting beneficial ownership of more than five percent of the class of
securities described in Item 1; and (2) has filed no amendment subsequent
thereto reporting beneficial ownership of five percent or less of such class.
(See Rule 13d-7.)

         NOTE: Six copies of this statement, including all exhibits, should be
filed with the Commission. See Rule 13d-1(a) for other parties to whom copies
are to be sent.

                                  Page 1 of 10





                              CUSIP NO. 79 8241105

- --------------------------------------------------------------------------------


(1)    Name of Reporting Person.  S.S. or I.R.S. Identification No. of Above
       Person

                 White Mountains Insurance Group, Inc. ("WMIG")
                                   94-2708455

- --------------------------------------------------------------------------------


(2)    Check the Appropriate Box if a Member (a) _____________ of a Group (See
       Instructions)
___________________________________(b)_______________

(3)    (SEC Use Only)

- --------------------------------------------------------------------------------


(4)    Source of Funds (See Instructions)

- --------------------------------------------------------------------------------


(5) Check if Disclosure of Legal Proceedings is Required Pursuant to Items 2(d)
or 2(e)

- --------------------------------------------------------------------------------


(6)    Citizenship or Place of Organization    DELAWARE

- --------------------------------------------------------------------------------


       Number of Shares             (7)   Sole Voting Power
       Beneficially Owned
       by Each Reporting                  --------------------------------------
       Person With                  (8)   Shared Voting Power
                                          1,764,376 Units of Beneficial Interest
                                          ("Units")
                                          --------------------------------------
                                    (9)   Sole Dispositive Power
                                          --------------------------------------
                                    (10)  Shared Dispositive Power
                                          1,764,376 Units of Beneficial Interest
                                          ("Units")

- --------------------------------------------------------------------------------


(11)   Aggregate Amount Beneficially Owned by Each Reporting Person
                                                     1,764,376 Units

- --------------------------------------------------------------------------------


(12)   Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See
       Instructions)

- --------------------------------------------------------------------------------


(13)   Percent of Class Represented by Amount in Row (11)
                                                     Approximately 3.8%

- --------------------------------------------------------------------------------


(14)   Type of Reporting Person (See Instructions)  HC, CO

                                  Page 2 of 10





                              CUSIP NO. 79 8241105

- --------------------------------------------------------------------------------


(1)    Name of Reporting Person.  S.S. or I.R.S. Identification No. of Above
       Person

                    White Mountains Properties, Inc. ("WMPI")
                   (formerly Fund American Enterprises, Inc.)
                                   02-0507896
- --------------------------------------------------------------------------------


(2)    Check the Appropriate Box if a Member (a) _____________ of a Group (See
       Instructions)
___________________________________(b)_______________

(3)    (SEC Use Only)

- --------------------------------------------------------------------------------


(4)    Source of Funds (See Instructions)

- --------------------------------------------------------------------------------


(5) Check if Disclosure of Legal Proceedings is Required Pursuant to Items 2(d)
or 2(e)

- --------------------------------------------------------------------------------


(6)    Citizenship or Place of Organization    DELAWARE

- --------------------------------------------------------------------------------


       Number of Shares             (7)   Sole Voting Power
       Beneficially Owned
       by Each Reporting                  --------------------------------------
       Person With                  (8)   Shared Voting Power
                                          1,764,376 Units
                                          --------------------------------------
                                    (9)   Sole Dispositive Power
                                          --------------------------------------
                                    (10)  Shared Dispositive Power
                                          1,764,376 Units

- --------------------------------------------------------------------------------


(11)   Aggregate Amount Beneficially Owned by Each Reporting Person
                                                     1,764,376 Units

- --------------------------------------------------------------------------------


(12)   Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See
       Instructions)

- --------------------------------------------------------------------------------


(13)   Percent of Class Represented by Amount in Row (11)
                                                     Approximately 3.8%

- --------------------------------------------------------------------------------


(14)   Type of Reporting Person (See Instructions)  HC, CO

                                  Page 3 of 10





ONLY ITEMS REPORTED IN THIS FINAL AMENDMENT TO SCHEDULE 13D ARE AMENDED
FROM THE FILING ON SCHEDULE 13D DATED DECEMBER 28, 1990 (THE "SCHEDULE 13D"),
AS AMENDED BY AMENDMENT NO. 1 DATED FEBRUARY 13, 1992, AMENDMENT NO. 2
DATED NOVEMBER 6, 1992, AMENDMENT NO. 3 DATED APRIL 27, 1993, AMENDMENT NO.4
DATED JUNE 23, 1993, AMENDMENT NO. 5 DATED JULY 7, 1993, AMENDMENT NO. 6 DATED
SEPTEMBER 2, 1993, AMENDMENT NO. 7 DATED DECEMBER 23, 1993, AMENDMENT NO. 8
DATED NOVEMBER 20, 1997, AMENDMENT NO. 9 DATED MARCH 25, 1999, AMENDMENT
NO. 10 DATED APRIL 13, 1999 AND AMENDMENT NO. 11 DATED JULY 7, 1999.  ALL OTHER
ITEMS REMAIN UNCHANGED.  UNLESS OTHERWISE SPECIFIED, ALL DEFINED TERMS
USED HEREIN HAVE THE MEANING PREVIOUSLY ASCRIBED TO THEM IN THE SCHEDULE
13D.

Item 4.  PURPOSE OF TRANSACTION.

         Consistent with WMIG's current strategy to redeploy its passive
investment portfolio into operating businesses (or to pursue other
opportunities), WMIG reserves the right to sell all or a portion of its Units at
any time and from time to time depending upon market conditions and other
factors affecting WMIG's evaluation of the value of the Units or its alternative
uses of the proceeds from sales of the Units.

Item 5. INTEREST IN SECURITIES OF THE ISSUER.

         Item 5 is hereby replaced in its entirety:

         (a) & (b) The aggregate number of Units and the percentage of the
outstanding Units owned by the indicated persons named in Item 2 is as follows:

                                  Page 4 of 10





Percentage of Units Units Beneficially Beneficially Person Owned Owned ------ ------------ ------------- WMIG 1,764,376 3.8% WMPI 1,764,376 3.8%
WMIG shares voting power and dispositive power with WMPI with respect to the 1,764,376 Units it holds indirectly through WMPI. Other than as set forth above, neither WMIG or WMPI, nor, to the best knowledge of WMIG or WMPI, any other persons named in Item 2 beneficially owns any Units. (c) There have been no transactions by WMIG or WMPI, or to the knowledge of WMIG or WMPI, any of the persons listed on Schedule I attached hereto, in Units of Beneficial Interest effected during the past 60 days, except as indicated in Schedule II attached hereto. (d) None (e) Not Applicable Page 5 of 10 SIGNATURE After reasonable inquiry and to the best of the knowledge and belief of the undersigned, the undersigned certifies that the information set forth in this statement is true, complete and correct. Dated: August 24, 1999 WHITE MOUNTAINS INSURANCE GROUP, INC. BY: ---------------------------------------- Name: Michael S. Paquette Title: Senior Vice President and Controller WHITE MOUNTAINS PROPERTIES, INC. BY: ---------------------------------------- Name: Michael S. Paquette Title: Senior Vice President and Controller Page 6 of 10 SCHEDULE I TO SCHEDULE 13D Following is a list of the directors and executive officers of White Mountains Insurance Group, Inc. ("WMIG") and White Mountains Properties, Inc. ("WMPI") setting forth the business address and present principal occupation or employment (and the name, principal business and address of any corporation or organization in which such employment is conducted) of each such person. Each such person is a citizen of the USA.
Name and Present Principal Business Address Office Occupation or Employment - ---------------- ------ ------------------------ WMIG Raymond Barrette Executive Vice President and Executive Vice President and WMIG Chief Financial Officer of Chief Financial Officer 80 South Main Street WMIG and WMPI, Hanover, NH 03755 Director of WMPI Terry L. Baxter Director and Executive Vice Executive Vice President WMIG President of WMIG and WMPI, 80 South Main Street Hanover, NH 03755 John J. Byrne Chairman of the Board Chairman of the Board WMIG 80 South Main Street Hanover, NH 03755 Patrick M. Byrne Director President Centricut, LLC of Centricut LLC 2 Technology Drive, STE 3 West Lebanon, NH 03784 Reid T. Campbell Vice President of WMIG Vice President WMIG and WMPI 80 South Main Street Hanover, NH 03755 Howard L. Clark, Jr. Director Vice Chairman of Lehman Lehman Brothers Inc. Brothers Inc. American Express Tower New York, NY 10128 Robert P. Cochran Director Chairman, President & Chief Financial Security Assurance Executive Officer of Holdings Ltd. Financial Security Assurance 350 Park Avenue Holdings Ltd. New York, NY 10022
Page 7 of 10 SCHEDULE I TO SCHEDULE 13D (CONT.)
Name and Present Principal Business Address Office Occupation or Employment - ---------------- ------ ------------------------ George J. Gillespie, III Director Partner in Cravath, Cravath, Swaine & Moore Swaine & Moore 825 Eighth Avenue New York, NY 10019 John D. Gillespie Director Managing Partner of Prospector Partners LLC Prospector Partners LLC 36 Trumbull Street Hartford, CT 06103 K. Thomas Kemp President, Chief Executive President and Chief Executive WMIG Officer & Director of WMIG Officer 80 South Main Street and WMPI, Chairman of WMPI Hanover, NH 03755 Gordon S. Macklin Director Retired 8212 Burning Tree Road Bethesda, MD 20817 Frank A. Olson Director Chairman of the Board & Chief The Hertz Corporation Executive Officer of The Hertz 225 Brae Boulevard Corporation Park Ridge, NJ 07656 Michael S. Paquette Sr. Vice President & Controller Sr. Vice President & Controller WMIG of WMIG and WMPI 80 South Main Street Hanover, NH 03755 David G. Staples Vice President Vice President WMIG of WMIG and WMPI 80 South Main Street Hanover, NH 03755 Arthur Zankel Director Co-Managing Partner, First Manhattan Co. First Manhattan Co., 437 Madison Ave. New York, N.Y. 10022
Page 8 of 10 WMPI Raymond Barrette* Terry L. Baxter* Reid T. Campbell* K. Thomas Kemp* Michael S. Paquette* * same as information provided above under WMIG Page 9 of 10 SCHEDULE II TO SCHEDULE 13D Sales of Units of San Juan Basin Royalty Trust by the Reporting Persons and by persons listed in Schedule I, within the last 60 days.
Sold by Date Number Sold Unit Price ------- ---- ----------- ---------- WMPI 7/6/99 27,700 8.00 WMPI 7/8/99 7,500 8.00 WMPI 7/15/99 5,000 8.00 WMPI 7/16/99 15,000 8.00 WMPI 7/2899 80,000 8.00 WMPI 7/30/99 31,000 8.00 WMPI 8/6/99 103,900 8.00 WMPI 8/10/99 69,700 8.00 WMPI 8/1199 18,700 8.00 WMPI 8/12/99 6,400 8.00 WMPI 8/13/99 10,000 8.00 WMPI 8/16/99 20,000 8.00 WMPI 8/1799 10,000 8.00 WMPI 8/18/99 41,600 8.00 WMPI 8/19/99 1,500,000 8.00
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