Ownership Submission
FORM 3
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  THORN WRAY T
2. Date of Event Requiring Statement (Month/Day/Year)
03/29/2007
3. Issuer Name and Ticker or Trading Symbol
Flagstone Reinsurance Holdings Ltd [FSR]
(Last)
(First)
(Middle)
FLAGSTONE REINSURANCE HOLDINGS LIMITED, 23 CHURCH STREET
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

HAMILTON, D0 HM11
6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)
2. Amount of Securities Beneficially Owned
(Instr. 4)
3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)
4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Shares 5,504,997
I (1) (2)
By Marathon Special Opportunity Master Fund, Ltd. (1) (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)
2. Date Exercisable and Expiration Date
(Month/Day/Year)
3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)
4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)
6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Restricted Share Units   (3)   (3) Common Shares 4,997 $ 0 (4) I (1) (2) By Marathon Special Opportunity Master Fund, Ltd. (1) (2)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
THORN WRAY T
FLAGSTONE REINSURANCE HOLDINGS LIMITED
23 CHURCH STREET
HAMILTON, D0 HM11
  X      

Signatures

/s/ Wray T. Thorn 03/29/2007
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The reporting person is a director of Flagstone Reinsurance Holdings Limited (the "Company"). The reporting person does not individually hold or otherwise beneficially own any securities of the Company. The reporting person is an employee of Marathon Asset Management, LLC (the "Investment Manager"), which serves as the investment manager of Marathon Special Opportunity Master Fund, Ltd. (the "Fund"). The Fund owns certain securities of the Company, all of which are subject to the sole voting and investment authority of the Investment Manager. Thus, for the purposes of Reg. Section 240.13d-3, the Investment Manager is deemed to beneficially own the securities of the Company held by the Fund, and the reporting person disclaims beneficial ownership of the securities of the Company held by the Fund.
(2) The Investment Manager, in its capacity as the holder of sole voting and investment authority of more than 5% of the common shares of the Company pursuant to Reg. 13d-3, separately files statements pursuant to Section 13 of the Securities Exchange Act of 1934, as amended. The reporting person's interest in the securities reported herein is limited to the extent of his pecuniary interest in the Fund, if any.
(3) The Restricted Share Units ("RSUs") vest 100% on the date of the grant.
(4) Each RSU represents the right to receive without payment to the Company, one newly-issued, fully paid and non-assessable common share of the Company, subject to the terms and conditions of the RSU Plan and the grant certificate evidencing each grant. In the discretion of the Compensation Committee, upon vesting the value of an RSU grant alternatively may be paid in cash, or partly in cash and partly in common shares.

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