Born 7 December 1888, the eldest child of Ernest Colquhoun, actuary, of 16 Westbourne Terrace, London, W, and his wife, née Simkin. He was educated at Charterhouse and Trinity College, Cambridge, and entered St George's Hospital Medical School in 1911. War broke out in August 1914, three months after he had qualified, and he served through it in the RAMC. He was an assistant surgeon at the 13th General Hospital in France, and a surgeon at the 37th General Hospital at Salonika 1916-17, and officer-in-command of the military hospitals at Richborough and Sandwich, Kent until 1919. Returning to St George's in 1920, he became house surgeon, surgical registrar, resident assistant surgeon, and surgeon to the urological department. He was appointed surgeon to the hospital in 1935, and was lecturer on surgery in the medical school. As a young man he had also been house physician at the Children's Hospital, Paddington Green. He practised privately at 44 Brook Street, W, and later at 53 Green Street, W, and lived at 1 Tregunter Road, The Boltons, SW. Colquhoun was twice married. He retired to Woodslee, Sway Road, Lymington, Hampshire, and died in a nursing-home on 22 November 1951, aged 62, survived by his second wife, Gwendoline Parker, whom he had married in 1937, and by the two sons of his first marriage.