SEC Form 3

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 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* 3I INVESTMENTS PLC (Last) (First) (Middle) 16 PALACE STREET (Street) LONDON X0 SW1E 5JD (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 03/30/2012	3. Issuer Name and Ticker or Trading Symbol GAIN Capital Holdings, Inc. [ GCAP ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director 10% Owner Officer (give title below) X Other (specify below) Member of 10% owner group	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

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 Stock	851,967	I	See footnote(1)

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: 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

Explanation of Responses:

1. On March 30, 2012, 851,967 shares previously owned directly by 3i Technology Partners III LP ("Technology Partners") were transferred to Mayflower L.P. ("Mayflower"), an affiliate of Technology Partners. 3i Investments plc is the manager of Mayflower and has sole investment authority over the shares held by Mayflower and may be deemed to have voting and dispositive power with respect to the shares of common stock held by Mayflower. 3i Investments plc disclaims beneficial ownership of the shares, except to the extent of its pecuniary interest, if any, therein.

Remarks:

	/s/ Alastair Richardson as authorized signatory of 3i Investments plc	07/12/2013
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
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