| Cover | Nov. 05, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 5, 2020 |
| Entity File Number | 1-37368 |
| Entity Registrant Name | ADAPTIMMUNE THERAPEUTICS PLC |
| Entity Central Index Key | 0001621227 |
| Entity Tax Identification Number | 00-0000000 |
| Entity Incorporation, State or Country Code | X0 |
| Entity Address, Address Line One | 60 Jubilee Avenue |
| Entity Address, Address Line Two | Milton Park |
| Entity Address, City or Town | Abingdon, Oxfordshire |
| Entity Address, Country | GB |
| Entity Address, Postal Zip Code | OX14 4RX |
| City Area Code | 44 |
| Local Phone Number | 1235 430000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | American Depositary Shares, each representing 6 Ordinary Shares, par value £0.001 per share |
| Trading Symbol | ADAP |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
