Born about 1903, Thornton was educated at St Andrew's University, qualifying in 1926. After working at the Middlesex and the London Hospital he entered the Colonial Medical Service, and was a civil surgeon successively in Iraq, Malaya and Cyprus. He took the Fellowship in June 1931. He settled later at 10 Mentone Terrace, Edinburgh, but died suddenly, in his early sixties, in Grenada, British West Indies on 4 March 1966, survived by his wife, Nancy Hamilton.