AMENDED TAX SHARING AGREEMENT

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                                                                    Exhibit 10.7

                          AMENDED TAX SHARING AGREEMENT

          AGREEMENT, dated as of January 1, 2005, by and between Alleghany
Insurance Holdings LLC, a Delaware limited liability company ("AIHL"), and
Darwin Professional Underwriters, Inc. ("Darwin').

                                   WITNESSETH:

          WHEREAS, AIHL is wholly-owned by Alleghany Corporation, a Delaware
corporation ("Alleghany"), and is treated as a "disregarded entity" for Federal
income tax purposes; and

          WHEREAS, Alleghany is the "common parent" corporation of an
"affiliated group" of corporations (the "Alleghany Group"), as those terms are
defined in Section 1504(a) of the Internal Revenue Code of 1986, as amended (the
"Code"), which group, by reason of Alleghany's ownership of AIHL, includes
Darwin, and any corporation that is or subsequently becomes a member of an
"affiliated group" of which Darwin would be the "common parent," as such terms
are defined in Section 1504(a) of the Code, if Darwin were owned by individuals
(Darwin and any current or future member of its affiliated group being referred
to herein as the "Darwin Group"); and

          WHEREAS, AIHL has agreed with Alleghany for determining on an
equitable basis the amount to be paid by AIHL to Alleghany on account of the
ownership by AIHL of any entity included in the Alleghany Group; and

          WHEREAS, AIHL and Darwin desire to agree on an equitable basis for
determining the amount to be paid by Darwin to AIHL on account of the inclusion
of the Darwin Group in the Alleghany Group; and that it may have under this
Agreement. Alleghany shall have full and sole responsibility and discretion in
handling, settling,

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compromising or contesting any tax audit or contest involving such Tax Claim;
provided, however, that at the time that Darwin is no longer a member of the
Alleghany Group, Alleghany shall keep Darwin informed as to the progress of any
tax audit or contest and, if requested by Darwin, shall consult with, and
consider in good faith any recommendation by, Darwin (or its counsel) concerning
the conduct of such tax audit or contest.

          1. Resolution of Disputes as to the Darwin Group's Hypothetical Tax.
In the event of a disagreement between the parties hereto as to the amount of
the Darwin Group's hypothetical tax for any taxable year covered by this
Agreement, such amount shall be determined by the independent certified public
accountants who audit the certified financial statements of Alleghany for such
taxable year, and the determination of such accountants shall be final and
binding on the parties hereto; provided, however, that if the independent
certified public accountants who audit the certified financial statements of
Alleghany for such taxable year are not permitted or are unwilling to resolve
any such disagreement, then Alleghany and Darwin shall submit such disagreement
to a mutually acceptable national accounting firm (which shall not be the
accountants who regularly audit the financial statements of Darwin), whose
decision shall be conclusive and binding on Alleghany and Darwin. Alleghany and
Darwin shall each pay one-half of the fees and expenses of such mutually
acceptable national accounting firm.

          2. Earnings and Profits and Characterization of Payments. Earnings and
profits of each member of the Alleghany Group shall be calculated by allocating
the federal income tax liability of the Alleghany Group to each member in
accordance with


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the method described in Section 1552(a)(2) of the Code and the applicable
Treasury Regulations thereunder.

          3. Termination of Membership in the Alleghany Group.

          (a) If Darwin should cease to be a member of the Alleghany Group at
any time, Darwin and AIHL agree that for income tax purposes the taxable period
of the Darwin Group which began on January 1 of the calendar year in which
Darwin ceases to be a member of the Alleghany Group shall be terminated as of
the close of business on the date Darwin ceases to be a member of the Alleghany
Group (the "Termination Date") in accordance with Treasury Regulations Section
1.1502-76(b)(1) and items of income, gain, loss, deduction or credit (other than
transactions properly allocable thereunder to the portion of the day after the
Termination Date shall occur) shall be apportioned based upon a closing of the
books for income tax purposes in accordance with Treasury Regulation Section
1.1502-76(b), as reasonably applied by Alleghany. No election shall be made
under Treasury Regulation Section 1.1502-76(b)(2)(ii) (relating to ratable
allocation of a year's items), and Treasury Regulation Section
1.150276(b)(2)(iii) will be applied to ratably allocate the items (other than
extraordinary items, including, without limiting the generality of the
foregoing, compensation items) for the month which includes the Closing Date.
All amounts attributable to any deferred intercompany transactions (as defined
in Treasury Regulation Section 1.1502-13) any "excess loss accounts" (as defined
in Treasury Regulation Section 1.1502-19) and other similar items among or
involving the members of the Darwin Group required to be taken into account at
the time Darwin ceases to be a member of the Alleghany Group shall be taken into
account in computing the Darwin Group's hypothetical tax for the taxable period
that


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includes the Termination Date. Darwin agrees to file all tax returns, handle the
contest of any audit and otherwise act for all Tax purposes consistent with the
provisions of this Section 7(a).

          (b) Except as otherwise expressly contemplated by this Agreement, from
and after the Termination Date, Darwin will not without the prior written
consent of Alleghany (which consent shall not be unreasonably conditioned,
delayed or withheld), directly or indirectly make, change or revoke, or permit
to be made, changed or revoked, any election or method of accounting with
respect to federal income taxes affecting the liability of the Darwin Group for
tax periods prior to the Termination Date or that is intended to be effective
prior to the Termination Date.

          (c) All of the obligations of Darwin under this Agreement shall
continue in full force and effect following the Termination Date notwithstanding
that neither Darwin nor the Darwin Group may be members of the Alleghany Group,
including without limiting the generality of the foregoing, Darwin's obligation
to pay AIHL any additional federal income taxes arising by reason of any
adjustments to the Darwin Group's hypothetical tax for any taxable year that
Darwin was a member of the Alleghany Group. All of the obligations of AIHL shall
be terminated effective as of the Termination Date, except the obligations of
AIHL under Sections 3(b), 3(e) and 9.

          (d) None of Darwin, the Darwin Group, or any affiliated group (within
the meaning of Section 1504(a) of the Code), which includes any member of the
Darwin Group shall claim in, or carryback to, any taxable year for which a
consolidated federal income tax return is or was filed by Alleghany any item of
loss, deduction or credit arising in any tax period beginning after the
Termination Date.


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          (e) Notwithstanding that Darwin may not have been paid for all of the
net