Thomas was living in Edmonton (like his future brother-in-law, George Albon, also a CO) when he was called up, aged 21, in 1916. He was a turner and fitter, trade unionist and member of the No-Conscription Fellowship. After adopting an absolutist position, he was imprisoned in Wormwood Scrubs and Wandsworth. By January 1919 he had served three sentences and spent more than two years in prison, and was finally released on medical grounds.