Thomas was born to a civil servant and a teacher, and has four siblings.[1] He is a grandson of historian Charles Thomas and writer Jessica Mann on his father's side, and a grandson of Christopher Brett, 5th Viscount Esher, on his mother's side.[2] He was educated at Winchester College and studied politics, religion and ethics at King's College London.[1] He learned to read and write in Arabic and studied abroad in Egypt shortly after the Arab Spring.[1]
Thomas was one of fourteen former services personnel standing as Labour candidates in the 2024 general election with him stating on his website that he was seeking to "neutralise Johnny Mercer's electoral 'trump card' of having a military service record" by running in his constituency of Plymouth Moor View.[6][7] Mercer accused Thomas of attempting to "bloat" his military record in a 2023 newspaper by The Guardian in which he claimed that he had "served in combat missions" and called him a "real life Walter Mitty in Plymouth".[4][8] Former defence minister Ben Wallace stated that serving "on operations or an operational tour is not necessarily the same as being in combat", and that he "[knew] exactly what the Labour candidate did in uniform and while he was on operations he was not himself in combat."[9]
Thomas said that, having recently served on sensitive operations, he was unable to discuss aspects of his military service and instead cited his certificate of valediction, signed by an unnamed Special Forces Support Group lieutenant colonel, which stated that he obtained "considerable operational experience" relative to how long he served and "lead personnel...in a range of hostile and challenging environments".[10][8]
On 4 July 2024, Thomas was elected as the Member of Parliament (MP) for Plymouth Moor View with 17,665 votes (41.2%), a majority of 5,604 over the second place Conservative candidate.[11]