Changes in Beneficial Ownership · 4

Arqit Quantum Inc.

ARQQNASDAQEQUITYCurrent

Changes in Beneficial Ownership

Filed Oct 7, 2026Accepted Oct 7, 2026, 7:44 PM EDTFiling CIK 1859690Accession 0001859690-26-000180

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Structured filing — 4

form4.xml

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Filing details

Report period: 2026-10-05
Issuer: Arqit Quantum Inc.
Issuer CIK: 0001859690
Trading symbol: ARQQ

Reporting owner 1

Name: Ritchie Garth
Reporting owner CIK: 0001840684
Relationship: Director
Address: 3 ORCHARD PLACE, LONDON, UNITED KINGDOM, X0, SW1H 0BF

Non-derivative transactions

Non-derivative transactions · 5 reported rows
Security	Transaction date	Code	Amount	A / D	Price (USD)	Owned after	Ownership
Ordinary Shares	2026-10-05	M · Form 4	16	A	0^[F1]	105,847	D
Ordinary Shares	2026-10-05	M · Form 4	66	A	0^[F1]	105,913	D
Ordinary Shares	2026-10-05	M · Form 4	83	A	0^[F1]	105,996	D
Ordinary Shares	2026-10-05	M · Form 4	83	A	0^[F1]	106,079	D
Ordinary Shares	2026-10-05	S · Form 4	127	D	23.7847	105,952	D

Table key

M · Form 4: Exempt derivative exercise or conversion under Rule 16b-3
A: Acquired
D: Direct
S · Form 4: Sale on the market or privately

Derivative transactions

Derivative transactions · 4 reported rows
Security	Conversion / exercise price (USD)	Transaction date	Code	Amount	A / D	Exercisable	Expires	Underlying security	Underlying shares	Owned after	Ownership
Restricted Share Units	^[F2]	2026-10-05	M · Form 4	16	D	^[F2]	^[F2]	Ordinary Shares	16	816	D
Restricted Share Units	^[F2]	2026-10-05	M · Form 4	66	D	^[F2]	^[F2]	Ordinary Shares	66	750	D
Restricted Share Units	^[F3]	2026-10-05	M · Form 4	83	D	^[F3]	^[F3]	Ordinary Shares	83	1,001	D
Restricted Share Units	^[F4]	2026-10-05	M · Form 4	83	D	^[F4]	^[F4]	Ordinary Shares	83	2,000	D

Table key

M · Form 4: Exempt derivative exercise or conversion under Rule 16b-3
D: Direct

Footnotes

F1: The Restricted Share Units ("RSUs") convert into ARQQ ordinary shares on a one-for-one basis.↩ 1 ↩ 2 ↩ 3 ↩ 4
F2: The RSUs vest quarterly in equal installments on October 1, 2026, and January 1, April 1, and July 1, 2027.↩ 1 ↩ 2 ↩ 3 ↩ 4 ↩ 5 ↩ 6
F3: The RSUs vest quarterly in equal installments on October 1, 2026, and January 1, April 1, July 1, and October 1, 2027.↩ 1 ↩ 2 ↩ 3
F4: The RSUs vest quarterly in equal installments on 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.↩ 1 ↩ 2 ↩ 3

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.

Signature 1

Signed: /s/ Noleen McDonnell, as Attorney-in-Fact
Date: 2026-10-07

Filed exhibits

POWER OF ATTORNEY (PUBLIC): POA JUN26 ↗doc1.txt

Company context

Arqit Quantum Inc. (Nasdaq: ARQQ) secures the world’s most critical data with quantum-safe encryption software. Simple, scalable, and compliant, its products integrate with existing infrastructure, and requires no rip and replace of hardware. Arqit provides a complete “Detect, Protect, Comply” solution for governments and enterprises that detects and inventories cryptographic assets, protects data, ensures compliance, and safeguards transition to the post-quantum era.

Current securities

ARQQNASDAQ · EQUITY · Current

Historical securities (1)

ARQQWNASDAQ · WARRANT · Historical · closed Sep 2, 2026

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