Born 28 December 1870 at Cwmmarch, Llandyssul, Cardiganshire, the eldest son of Griffith Thomas, FRCVS, and Jane Jenkins, his wife. He was educated at Cilian Park School near Aberayron, Cardiganshire, at the Newquay Grammar School, Cardiganshire, and at University College, Aberystwyth. He entered the Guy's Hospital Medical School, graduating at the London University with first-class honours in materia medica and with honours in anatomy at the intermediate MB examination, acted as house surgeon at the Hospital, and as assistant demonstrator of anatomy in the Medical School. He then joined his uncle Dr (afterwards Sir) Abraham Garrod Thomas, MRCS 1876, in general practice at Newport, Monmouthshire, and was soon appointed surgeon to the local charity, known later as the Royal Gwent Hospital. On 30 December 1908 he joined the newly founded Territorial Force with a commission as captain *à la suite*, RAMC(T), was mobilized with the rank of major on 12 June 1915, and was attached to the 3rd Western General Hospital. After the war of 1914-18 he became consulting surgeon to the Welsh National Memorial Hospital. He was also visiting surgeon to the Monmouthshire and Newport Mental Hospitals, president of the Newport Medical Society, and the representative of London University on the governing body of the University of Wales. He married Eileen Kathleen Green on 26 April 1906. She survived him with a son, a medical student (1939) at Guy's Hospital, and a daughter. He died at Newport, Monmouthshire on 9 October 1939. Although Thomas preferred to call himself a general practitioner his practice and inclination lay really in surgery, both general and ophthalmic. He had a large practice and was instrumental in maintaining a high standard throughout his sphere of influence.