<PAGE>

                                                                   Exhibit 10.12
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                           NEWS AMERICA INCORPORATED,

                                              Company,

                         THE NEWS CORPORATION LIMITED,
                           FOX BROADCASTING COMPANY,
                        FOX ENTERTAINMENT GROUP, INC.,
                        FOX TELEVISION HOLDINGS, INC.,
                        HARPERCOLLINS PUBLISHERS INC.,
                              HARPERCOLLINS (UK),
                     THE HERALD AND WEEKLY TIMES LIMITED,
                         NATIONWIDE NEWS PTY. LIMITED,
                       NEWS AMERICA MARKETING FSI, INC.,
                        NEWS GROUP NEWSPAPERS LIMITED,
                            NEWS INTERNATIONAL plc,
                                 NEWS LIMITED,
                      NEWS PUBLISHING AUSTRALIA LIMITED,
                             NEWS SECURITIES B.V.,
                           NEWS T INVESTMENTS, INC.,
                         NEWS TRIANGLE FINANCE, INC.,
                             NEWSCORP INVESTMENTS,
                          NEWSCORP OVERSEAS LIMITED,
                    TWENTIETH CENTURY FOX FILM CORPORATION,
                TWENTIETH CENTURY FOX HOME ENTERTAINMENT, INC.,

                                              Guarantors

                                      and

                      STATE STREET BANK AND TRUST COMPANY
             (as successor to THE FIRST NATIONAL BANK OF BOSTON),

                                              Trustee

                           ________________________


                         TENTH SUPPLEMENTAL INDENTURE
                           Dated as of March 2, 2000

                   Amending and Supplementing the Indenture
                          Dated as of January 28, 1993
                           ________________________

                               Senior Securities

================================================================================
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     TENTH SUPPLEMENTAL INDENTURE, dated as of March 2, 2000, among News America
Incorporated, a Delaware corporation (the "Company") with its principal office
located at 1211 Avenue of the Americas, New York, New York 10036, The News
Corporation Limited, a South Australia, Australia corporation (A.C.N. 007 910
330) ("News Corporation"), Fox Broadcasting Company, Fox Entertainment Group,
Inc., Fox Television Holdings, Inc., HarperCollins Publishers, Inc.,
HarperCollins (UK), The Herald and Weekly Times Limited, Nationwide News Pty.
Limited, News America Marketing FSI, Inc., News Group Newspapers Limited, News
International plc, News Limited, News Publishing America Limited, News
International plc, News Limited, News Publishing Australia Limited, News
Securities B.V., News T Investments, Inc., News Triangle Finance, Inc., Newscorp
Investments, Newscorp Overseas Limited, Twentieth Century Fox Film Corporation,
Twentieth Century Fox Home Entertainment, Inc., and State Street Bank and Trust
Company, a national banking association, as successor to The First National Bank
of Boston (the "Trustee"), amending and supplementing the Indenture, dated as of
January 28, 1993 (the "Original Indenture"), among the Company, the guarantors
named therein (collectively, the "Guarantors") and the Trustee, which provided
for the issuance from time to time of the Company's senior debt securities, to
be issued in one or more series as provided therein (the "Securities").  (The
Original Indenture as supplemented by the First Supplemental Indenture, dated as
of March 24, 1993, the Second Supplemental Indenture, dated as of April 8, 1993,
the Third Supplemental Indenture, dated as of May 20, 1993, the Fourth
Supplemental Indenture, dated as of May 28, 1993, the Fifth Supplemental
Indenture, dated as of July 21, 1993, the Sixth Supplemental Indenture, dated as
of January 25, 1994, the Seventh Supplemental Indenture, dated as of February 4,
1994, the Eighth Supplemental Indenture, dated as of May 12, 1994, the Ninth
Supplemental Indenture, dated as of August 1, 1995, and this Tenth Supplemental
Indenture and as may hereafter be supplemented is referred to herein as the or
this "Indenture").  Capitalized terms used herein and not otherwise defined
herein have the meanings ascribed thereto in the Indenture.


                                   RECITALS:

     WHEREAS, effective December 31, 1997 two Guarantors under the Indenture,
News America Publishing Incorporated ("NAPI") and Fox, Inc. ("Fox"), were merged
into the Company and upon such merger the separate corporate existence of NAPI
and Fox ceased and the Company remained in existence as the Surviving
Corporation;

     WHEREAS, effective January 2, 1998, the Company changed its name to News
America Incorporated;

     WHEREAS, effective June 30, 1998, News America FSI, Inc., a Guarantor under
the Indenture, changed its name to News America Marketing FSI, Inc.; effective
August 11, 1998, Twentieth Holdings Corporation, a Guarantor under the
Indenture, changed its name to Fox Entertainment Group, Inc.; effective October
24, 1998, Fox Television Stations, Inc., a Guarantor under the Indenture,
changed its name to Fox Television Holdings, Inc.; and effective January 22,
1999, Newscorp Investments Limited, a Guarantor under the Indenture, changed its
name to Newscorp Investments; and

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     WHEREAS, effective March 1, 1999, all of the stock of News America
Publications Inc., a Guarantor under the Indenture, was sold by News
Corporation, and upon such sale, News America Publications Inc. ceased to be a
Guarantor under Indenture; and

     WHEREAS, the provisions of this Tenth Supplemental Indenture shall not
adversely affect the interests of the Holders of Securities in any material
respect; and

     WHEREAS, the Original Indenture is subject to the provisions of the United
States Trust Indenture Act of 1939, as amended (the "TIA"), that are required to
be part of the Original Indenture and the Indenture shall, to the extent
applicable, be governed by such provisions; and

     WHEREAS, the Company has duly authorized the execution and delivery of this
Tenth Supplemental Indenture and has done all things necessary to make this
Tenth Supplemental Indenture a valid agreement in accordance with its terms.

     NOW, THEREFORE, THIS INDENTURE WITNESSETH:

     For and in consideration of the premises and the purchase of the Securities
by the Holders thereof, it is mutually covenanted and agreed, for the equal and
proportionate benefit of all Holders of the Securities, as follows:


                                  ARTICLE ONE

                              ORIGINAL INDENTURE

     SECTION 101.  Effect of Original Indenture.
                   ----------------------------

     Except as specifically provided in this Tenth Supplemental Indenture, the
Original Indenture, as heretofore supplemented and amended, shall remain in full
force and effect.


                                  ARTICLE TWO

                          AMENDMENTS TO THE INDENTURE

     SECTION 201.  Elimination of Guarantors.
                   --------------------------

     In accordance with Section 801 of the Original Indenture, each of the
following entities is hereby eliminated as a Guarantor under the Indenture:

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     Name                           Jurisdiction of Incorporation
     ----                           -----------------------------

Fox, Inc.                                     Colorado
News America Publishing Incorporated          Delaware
News America Publications Inc.                Delaware

     SECTION 202.   Change of Name of the Company and Certain Guarantors.
                    -----------------------------------------------------

     In accordance with Section 801 of the Original Indenture, the name of the
Company is hereby changed to News America Incorporated, Inc., the name of News
America FSI, Inc. is hereby changed to News America Marketing FSI, Inc., the
name of Twentieth Holdings Stations, Inc. is hereby changed to Fox Entertainment
Group, Inc., the name of Fox Television Stations, Inc. is hereby changed to Fox
Television Holdings, Inc. and the name of Newscorp Investments Limited is hereby
changed to Newscorp Limited.


     SECTION 203.   References in the Indenture.
                    ----------------------------

     By reason of the elimination of certain Guarantors pursuant to Section 201
hereof, the name change of four Guarantors pursuant to Section 202 hereof and
the continuation, as Guarantors, of the Guarantors under the Indenture, all
references in the Indenture to the "Guarantors" are hereby deemed to refer to
the following entities and all such references to each or any "Guarantor" are
hereby deemed to refer to each of such entities:

     Name                           Jurisdiction of Incorporation
     ----                           -----------------------------

The News Corporation Limited                  South Australia, Australia
Fox Broadcasting Company                      Delaware
Fox Entertainment Group, Inc.                 Delaware
Fox Television Holdings, Inc.                 Delaware
HarperCollins Publishers Inc.                 Delaware
HarperCollins (UK)                            England
The Herald and Weekly Times Limited           Victoria, Australia
Nationwide News Pty. Limited                  Australian Capital
                                               Territory, Australia
News America Marketing FSI, Inc.              Delaware
News Group Newspapers Limited                 England
News International plc                        England
News Limited                                  South Australia, Australia
News Publishing Australia Limited             Delaware
News Securities B.V.                          Netherlands
News T Investments, Inc.                      Delaware
News Triangle Finance, Inc.                   Delaware
Newscorp Investments                          England

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Newscorp Overseas Limited                         Cayman Islands,
                                                   British West Indies
Twentieth Century Fox Film Corporation            Delaware
Twentieth Century Fox Home Entertainment, Inc.    Michigan


     SECTION 204.   Change of Definition of "Fox Group."
                    ------------------------------------

     In accordance with Section 801 of the Original Indenture, the definition of
"Fox Group" set forth in Section 101 of the Original Indenture is hereby amended
by deleting the existing definition thereof and substituting therefor the
following:

          "Fox Group" means Fox Entertainment Group, Inc., a Delaware
          corporation and its respective consolidated Restricted Subsidiaries.


     SECTION 203.   Change of Definition of "Subsidiary."
                    -------------------------------------

     In accordance with Section 801 of the Original Indenture, the definition of
"Subsidiary" set forth in Section 101 of the Original Indenture is hereby
amended by deleting the existing definition thereof and substituting therefor
the following:

     "Subsidiary" is defined as, with respect to any Person, (i) a corporation a
     majority of whose capital stock with voting power, under ordinary
     circumstances, to elect directors is at the time, directly or indirectly,
     owned by such Person, by one or more Subsidiaries of such Person or by such
     Person and one or more Subsidiaries thereof or (ii) any other Person (other
     than a corporation) in which such Person, one or more Subsidiaries thereof
     or such Person and one or more Subsidiaries thereof, directly or
     indirectly, at the date of determination thereof has at least a majority
     ownership interest and the power to direct the policies, management and
     affairs thereof and shall, with respect to News Corporation and NAI,
     include Fox Television Holdings, Inc. and its Subsidiaries and their
     successors. For purposes of this definition, any director's qualifying
     shares or investments by foreign nationals mandated by applicable law shall
     be disregarded in determining the ownership of a Subsidiary.


                                 ARTICLE THREE

                                 MISCELLANEOUS

     SECTION 301.   Effect of Headings.
                    ------------------

     The Article and Section headings herein are for convenience of reference
only and shall not effect the construction hereof.

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     SECTION 302.   Governing Law.
                    -------------

     Subject to the following sentence, this Tenth Supplemental Indenture shall
be governed by, and construed in accordance with, the laws of the State of New
York, without regard to principles of conflicts of laws.  This Tenth
Supplemental Indenture is subject to the provisions of the TIA that are required
to be part of the Original Indenture and shall, to the extent applicable, be
governed by such provisions.


     SECTION 303.   Counterparts.
                    ------------

     This Tenth Supplemental Indenture may be executed in any number of
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

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     IN WITNESS WHEREOF, the parties hereto have caused this Tenth Supplemental
Indenture to be duly executed as of the day and year first above written.

                                 News America Incorporated



                                 By: /s/ Arthur M. Siskind
                                    ---------------------------------------
                                   Name: Arthur M. Siskind
                                   Title: Senior Executive Vice President



                                 Executed as a Deed in New York,
                                 New York


                                 The News Corporation Limited,
                                        as Guarantor


                                 Fox Broadcasting Company,
                                        as Guarantor


                                 Fox Entertainment Group, Inc.
                                        as Guarantor


                                 Fox Television Holdings, Inc.,
                                        as Guarantor


                                 HarperCollins Publishers Inc.,
                                        as Guarantor


                                 HarperCollins (UK),
                                        as Guarantor

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                                 The Herald and Weekly Times Limited,
                                        as Guarantor


                                 Nationwide News Pty. Limited,
                                        as Guarantor


                                 News America Marketing FSI, Inc.,
                                        as Guarantor


                                 News Group Newspapers Limited,
                                        as Guarantor


                                 News International plc,
                                        as Guarantor


                                 News Limited,
                                        as Guarantor


                                 News Publishing Australia Limited,
                                        as Guarantor


                                 News Securities B.V.,
                                        as Guarantor


                                 News T Investments, Inc.,
                                        as Guarantor


                                 News Triangle Finance, Inc.,
                                        as Guarantor


                                 Newscorp Investments,
                                        as Guarantor

                                      -8-
<PAGE>

                                 Newscorp Overseas Limited,
                                        as Guarantor


                                 Twentieth Century Fox Film Corporation,
                                        as Guarantor


                                 Twentieth Century Fox Home
                                 Entertainment, Inc.,
                                        as Guarantor



                                 By: /s/ Arthur M. Siskind
                                     -----------------------------------------
                                     Name:  Arthur M. Siskind
                                     Title: Senior Executive Vice President,
                                            News America
                                            Incorporated, as Attorney
                                            for the Guarantors

                                      -9-
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                                 State Street Bank and Trust Company,
                                        as Trustee


                                 By: /s/ Ruth A. Smith
                                    ----------------------------
                                      Name:  Ruth A. Smith
                                      Title: Vice President


     [seal]

Attest:
       --------------------------

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STATE OF NEW YORK   )
                    )  :  ss.:
COUNTY OF NEW YORK  )

     On this 8 day of March, 2000, before me personally appeared Arthur M.
Siskind who acknowledged himself to be a Senior Executive Vice President of News
America Incorporated, and that he, as such Senior Executive Vice President,
being authorized so to do, executed the foregoing instrument for the purposes
therein contained, by signing the name of the corporation by himself as such
Senior Executive Vice President.

     IN WITNESS WHEREOF, I hereunto set my hand and official seal.



/s/ Angela D. Weissert

Notary Public


                           Angela D. Weissert
[Notarial Seal]     Notary Public, State of New York
                             No. 41-4956083
                       Qualified in Nassau County
                    Commission Expires Sept. 11, 2001

                                      -11-
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STATE OF MASSACHUSETTS )
                       ) :  ss.:
COUNTY OF SUFFOLK      )

     On the 16/th/ day of May, 2000, before me personally came Ruth A. Smith, to
me known, who, being by me duly sworn, did depose and say that s/he is a Vice
President of State Street Bank and Trust Company, the national banking
association described in and which executed the foregoing instrument by
authority of the Board of Directors of said national banking association, and
that s/he signed her/his name thereto by like authority.

     IN WITNESS WHEREOF, I hereunto set my hand and official seal.

/s/ James M. Coolidge

Notary Public


[Notarial Seal]                      JAMES M. COOLIDGE
                                       Notary Public
                            My Commission Expires June 19, 2003



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