1
                       [HAYNES AND BOONE, LLP LETTERHEAD]


                                                                     EXHIBIT 5.1


                               September 22, 2000


HCC Insurance Holdings, Inc.
13403 Northwest Freeway
Houston, Texas  77040-6094

Ladies and Gentlemen:

         We have acted as counsel for HCC Insurance Holdings, Inc., a Delaware
corporation (the "Company") with respect to certain legal matters in connection
with the registration by the Company, under the Securities Act of 1933, as
amended (the "Securities Act"), of the offer and sale by the Company from time
to time, pursuant to Rule 415 under the Securities Act, of (1) unsecured debt
securities of the Company, which may be either senior or subordinated and may be
issued in one or more series, consisting of notes, debentures or other evidences
of indebtedness (the "Debt Securities"), (2) shares of common stock, $1.00 par
value, of the Company (the "Common Stock") and (3) warrants for the purchase of
Common Stock (the "Warrants" and, together with the Debt Securities and the
Common Stock, the "Securities").

         This opinion is further delivered in connection with the offer and sale
by the Company and HCC Capital Trust I and HCC Capital Trust II, each a business
trust formed under the Business Trust Act of the state of Delaware (each an "HCC
Trust", and collectively, the "HCC Trusts" and together with the Company, the
"Registrants") in connection with registration under the Securities Act by the
Registrants of (1) preferred securities of each of the HCC Trusts (the "Trust
Preferred Securities"); (2) guarantees by the Company of any Trust Preferred
Securities issued by each HCC Trust pursuant to a Guarantee Agreement to be
executed by the Company (the "Guarantees"); and (3) unsecured debt securities of
the Company (the "Trust Debt Securities"). The Trust Debt Securities, the Trust
Preferred Securities and the Guarantees are collectively referred to herein as
the "Offered Trust Securities."

         The aggregate initial offering price of the Securities and the Offered
Trust Securities to be offered and sold by Registrants, pursuant to a
registration statement on Form S-3 (the "Registration Statement"), to which this
opinion is an exhibit, will not exceed $300,000,000. The Securities will be
offered in amounts, at prices, and on terms to be determined in light of market


   2


HCC Insurance Holdings, Inc.
September 22, 2000
Page 2


conditions at the time of sale and to be set forth in supplements to the
prospectus (each a "Prospectus Supplement") contained in the Registration
Statement.

         We have examined originals or copies, certified or otherwise identified
to our satisfaction, of (1) the Certificate of Incorporation and Bylaws of the
Company, each as amended and/or restated to the date hereof, (2) the
Registration Statement, (3) the organizational documents of each of the HCC
Trusts; and (4) such other certificates, statutes, instruments and documents as
we considered appropriate for purposes of the opinions hereafter expressed. In
addition, we have further examined (1) the proposed form of Indenture for Trust
Debt Securities or Debt Securities from the Company to First Union National
Bank, as Trustee (the "Indenture") providing for the issuance of the Trust Debt
Securities or Debt Securities from time to time in one or more series pursuant
to the terms of one or more Securities Resolutions (as defined in the Indenture)
creating such series; (2) Trust Agreements among the Company, First Union
National Bank, as Property Trustee and First Union Trust Company, N.A., as
Delaware Trustee (the "Trust Agreements"); (3) other exhibits to the
Registration Statement relating to the Securities and the Offered Trust
Securities; and (4) corporate proceedings of the Registrants relating to the
Registration Statement, the Indenture, the Trust Agreements, the Guarantees and
the transactions contemplated thereby. In addition, we reviewed such questions
of law we considered appropriate.

         In connection with this opinion, we have assumed that (i) the
Registration Statement, and any amendments thereto (including post-effective
amendments), will have become effective; (ii) a Prospectus Supplement will have
been prepared and filed with the Securities and Exchange Commission (the
"Commission") describing the Securities or Offered Trust Securities offered
thereby; (iii) all Securities and Offered Trust Securities will be issued and
sold in compliance with applicable federal and state securities laws and in the
manner stated in the Registration Statement and the applicable Prospectus
Supplement; (iv) the Indentures, a warrant agreement ("Warrant Agreement")
relating to the Warrants, each Trust Agreement and the Guarantees will each be
duly authorized, executed and delivered by the parties thereto; (v) each person
signing an Indenture, a Warrant Agreement, a Trust Agreement and a Guarantee
will have the legal capacity and authority to do so; (vi) at the time of any
offering or sale of any shares of Common Stock, that the Company shall have such
number of shares of Common Stock, as set forth in such offering or sale,
authorized or created and available for issuance; (vii) a definitive purchase,
underwriting or similar agreement with respect to any Securities or Offered
Trust Securities offered will have been duly authorized and validly executed and
delivered by the Company and


   3


HCC Insurance Holdings, Inc.
September 22, 2000
Page 3


the other parties thereto; and (viii) any Securities or Offered Trust Securities
issuable upon conversion, exchange or exercise of any Debt Securities, Warrant
or Trust Debt Securities being offered will have been duly authorized, created
and, if appropriate, reserved for issuance upon such conversion, exchange or
exercise.

         Based on the foregoing, and subject to the assumptions, qualifications,
limitations, and exceptions set forth herein, we are of the opinion that:

         (i)      When (a) the applicable Indenture relating either to senior
                  Debt Securities, subordinated Debt Securities or Trust Debt
                  Securities has been duly qualified under the Trust Indenture
                  Act of 1939, as amended, (b) the Board of Directors of the
                  Company (or a committee thereof) and/or the HCC Trusts has
                  taken all necessary corporate or similar action to approve the
                  issuance and terms of any such Debt Securities or Trust Debt
                  Securities or Guarantee, (c) the terms of such Debt Securities
                  or Trust Debt Securities or Guarantee and of their issuance
                  and sale have been duly established in conformity with the
                  applicable Indenture so as not to violate any applicable law
                  or result in a default under or breach of any agreement or
                  instrument binding upon the Company or the HCC Trusts and so
                  as to comply with any requirements or restrictions imposed by
                  any court or governmental body having jurisdiction over the
                  Company or the HCC Trusts, (d) any shares of Common Stock
                  issuable upon the conversion of such Debt Securities or Trust
                  Debt Securities, if applicable, have been duly and validly
                  authorized for issuance and (e) such Debt Securities or Trust
                  Debt Securities have been duly executed and authenticated in
                  accordance with the applicable Indenture and issued and sold
                  as contemplated in the Registration Statement, such Debt
                  Securities, Trust Debt Securities or Guarantee will constitute
                  valid and legally binding obligations of the Company and/or
                  the applicable HCC Trust respectively, subject to bankruptcy,
                  insolvency (including, without limitation, all laws relating
                  to fraudulent transfers), reorganization, moratorium and
                  similar laws relating to or affecting creditors' rights
                  generally and to general equitable principles (regardless of
                  whether enforcement is sought in a proceeding in equity or at
                  law), and the qualification that the remedy of specific
                  performance and injunctive or other forms of equitable relief
                  may be subject to equitable defenses and to the discretion of
                  the court before which any proceeding may be brought.



   4


HCC Insurance Holdings, Inc.
September 22, 2000
Page 4

         (ii)     When (a) the terms of any Warrant and of their issuance and
                  sale have been duly established in conformity with the
                  applicable Warrant Agreement so as not to violate any
                  applicable law or result in a default under, or breach of, any
                  agreement or instrument binding upon the Company and so as to
                  comply with any requirements or restrictions imposed by any
                  court or governmental body having jurisdiction over the
                  Company, and (b) the Warrants have been duly executed and
                  authenticated in accordance with the applicable Warrant
                  Agreement and issued and sold as contemplated in the
                  Registration Statement, the Warrants will constitute valid and
                  legally binding obligations of the Company, subject to
                  bankruptcy, insolvency (including, without limitation, all
                  laws relating to fraudulent transfers), reorganization,
                  moratorium and similar laws relating to or affecting
                  creditors' rights generally and to general equitable
                  principles (regardless of whether enforcement is sought in a
                  proceeding in equity or at law.

         (iii)    The Common Stock when authorized and sold as contemplated in
                  the Registration Statement, will be duly authorized, validly
                  issued, fully-paid and non-assessable.

         As to the legality of the Trust Preferred Securities to be issued by
the HCC Trusts, you are receiving the opinion of Richards, Layton & Finger,
special Delaware counsel to the HCC Trusts and the Company.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the use of our name in the Prospectus forming a
part of the Registration Statement and to the filing of this opinion as Exhibit
5 to the Registration Statement. In giving this consent, we do not admit that we
are within the category of persons whose consent is required under Section 7 of
the Securities Act and the rules and regulations thereunder.

                                                     Very truly yours,

                                                     HAYNES AND BOONE, LLP


                                                     /s/ HAYNES AND BOONE
                                                     ---------------------------