Exhibit 24.3

                                POWER OF ATTORNEY
                      for Aspen Insurance Holdings Limited
             Registration Statement on Form F-1 and Related Filings

     KNOW ALL MEN by these presents, that Ian Cormack does hereby make,
constitute and appoint Christopher O'Kane and Julian Cusack, and each of them,
as true and lawful attorney-in-fact and agent of the undersigned, with full
power of substitution, resubstitution and revocation, for and in the name, place
and stead of the undersigned, to execute and deliver a registration statement on
Form F-1 of Aspen Insurance Holdings Limited with the Securities and Exchange
Commission of the United States of America under the provisions of the
Securities Act of 1933, including any and all amendments to such registration
statement, a prospectus or an amended prospectus therein and any registration
statement for the same offering that is to be effective upon filing pursuant to
Rule 462(b) under the Securities Act, and all other documents in connection
therewith to be filed with the Securities and Exchange Commission; such
registration statement and each such amendment or document to be in such form
and to contain such terms and provisions as said attorney or substitute shall
deem necessary or desirable; giving and granting unto said attorney-in-fact, or
to such person or persons as in any case may be appointed pursuant to the power
of substitution herein given, full power and authority to do and perform any and
every act and thing whatsoever requisite, necessary or, in the opinion of said
attorney or substitute, able to be done in and about the premises as fully and
to all intents and purposes as the undersigned might or could do if personally
present, hereby ratifying and confirming all that said attorney or such
substitute shall lawfully do or cause to be done by virtue hereof.


     IN WITNESS WHEREOF, the undersigned has duly executed this power of
attorney on this 17th day of October, 2003.


                                                  By:      /s/ Ian Cormack
                                                        ------------------------
                                                  Name:    Ian Cormack
                                                  Title:   Director