Educated at Selwyn College, Cambridge, he took second-class honours in the Natural Sciences Tripos part I, 1902. After training at St Thomas's Hospital, where he won the University scholarship in 1904 and held house appointments, he settled in practice at Yeovil, Somerset and became surgeon to the Crewkerne and Yeovil Hospitals. During the war of 1914-18 he was a surgeon specialist at the 14th General Hospital, Boulogne with the rank of Captain RAMC. Unwin was chairman of the East Somerset division and President of the Dorset and West Hants branch of the British Medical Association. He lived at The Small House, Dorchester Road, Yeovil and died on 17 March 1964 aged 83, survived by his wife.