EXHIBIT 31.1

CERTIFICATION PURSUANT TO RULE 13a-14 OR 15d-14 UNDER

THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

I, Adrian Rawcliffe certify that:

1. I have reviewed this Amendment No. 1 to the Quarterly Report on Form 10-Q of Adaptimmune Therapeutics plc; and

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.