Achilles Therapeutics plc Instructions to The Bank of New York Mellon, as Depositary (Must be received prior to 5:00 p.m.
on June 22, 2022) The undersigned Holder of American Depositary Receipts (ADRs) hereby acknowledges receipt of a Notice to Holders from the Depositary and hereby requests and instructs The Bank of New York Mellon, as Depositary, to endeavor, insofar
as practicable, to vote or cause to be voted the number of shares or other Deposited Securities represented by such ADRs of Achilles Therapeutics plc (the Company) registered in the name of the undersigned on the books of the Depositary as of the
close of business on May 19, 2022 at the Companys Annual General Meeting to be held on Tuesday, June 28, 2022 at 17:00 UK time (12:00 Eastern Time), on the matters specied on the reverse side. NOTE: 1. Instructions as to voting on specified
resolutions should be indicated by placing an X in the appropriate box. 2. Pursuant to Section 4.7 of the Deposit Agreement, the Depositary shall not vote or attempt to exercise the right to vote that attached to the deposited Shares other than in
accordance with instructions given by Owners and received by the Depositary or as provided in the following sentence. If the Depositary has received from the Company by June 18, 2022 a written conrmation that, as of the June 18, 2022, (x) the
Company wishes a proxy to be given under this sentence, (y) the Company reasonably does not know of any substantial opposition to the matters and (z) the matters are not materially adverse to the interests of shareholders. (Continued and to be
marked, dated and signed, on the other side) PROXY TABULATOR FOR ACHILLES THERAPEUTICS PLC P.O. Box 8016 CARY, NC 27512-9903
