Form: 3

Initial statement of beneficial ownership of securities

March 18, 2026

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*
Lefebvre d'Ovidio Manfredi

(Last) (First) (Middle)
C/O ARQIT INC.
1209 ORANGE STREET

(Street)
WILMINGTON DE 19801

(City) (State) (Zip)
2. Date of Event Requiring Statement (Month/Day/Year)
03/18/2026
3. Issuer Name and Ticker or Trading Symbol
Arqit Quantum Inc. [ ARQQ ]
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 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)
Ordinary Shares 37,241 D
Ordinary Shares 4,396,891 I beneficially owned through Heritage Assets SCSP
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
Business Combination Warrants (right to buy) (1) 09/03/2026 Ordinary Shares 29,864.72 (1) I beneficially owned through Heritage Assets SCSP
Ordinary Share Purchase Warrants (right to buy) (2) 09/30/2026 Ordinary Shares 4,600,000 2.5 I beneficially owned through Heritage Assets SCSP
Ordinary Share Purchase Warrants (right to buy) (2) 09/12/2028 Ordinary Shares 230,769 19.5 I beneficially owned through Heritage Assets SCSP
Restricted Stock Units (3) (3) Ordinary Shares 100 (3) D
Restricted Stock Units (4) (4) Ordinary Shares 21,496 (4) D
Restricted Stock Units (5) (5) Ordinary Shares 1,751 (5) D
Restricted Stock Units (6) (6) Ordinary Shares 3,000 (6) D
Explanation of Responses:
1. Each Business Combination Warrant has an exercise price of $11.50 and can be exercised at any time, at the holder's election, to purchase 0.04 of an ARQQ ordinary share, and cannot be exercised for fractional shares. Accordingly, holders of Business Combination Warrants are required to exercise at least 25 Business Combination Warrants in order to receive one whole ARQQ ordinary share at an aggregate exercise price of $287.50 per whole ARQQ ordinary share. The reporting person beneficially owns 746,618 Business Combination Warrants, which, if exercised in full, would be equivalent to 29,864.72 ARQQ ordinary shares.
2. Each Ordinary Share Purchase Warrant can be exercised at any time, at the holder's election, to purchase one ARQQ ordinary share.
3. Each Restricted Stock Unit ("RSU") represents a contingent right to receive one ARQQ ordinary share. The RSUs vest quarterly in equal installments on April 1, and July 1, 2026.
4. Each RSU represents a contingent right to receive one ARQQ ordinary share. The RSUs vest quarterly in equal installments on April 1, July 1, and October 1, 2026, and January 1, April 1, and July 1, 2027.
5. Each RSU represents a contingent right to receive one ARQQ ordinary share. The RSUs vest quarterly in equal installments on April 1, July 1, and October 1, 2026, and January 1, April 1, July 1, and October 1, 2027.
6. Each RSU represents a contingent right to receive one ARQQ ordinary share. 501 RSUs vest on April 1, 2026 and the remaining RSUs vest quarterly in equal installments on July 1, and October 1, 2026, and January 1, April 1, July 1, and October 1, 2027, and January 1, April 1, July 1, and October 1, 2028.
Remarks:
Due to the issuer's status as a foreign private issuer pursuant to Rule 3a12-3(b) under the Securities Exchange Act of 1934 (the "Act"), the reporting person's transactions in the issuer's securities are exempt from Sections 16(b) and 16(c) of the Act. Ex. 24 - Power of Attorney
/s/ Noleen McDonnell, as Attorney-in-Fact 03/18/2026
** 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).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.