 Digby was born in Ealing, London, the son of William Digby (writer), who was in the Indian Civil Service.He was the cousin of Kenelm Hubert Digby, the proposer of the notorious 1933 "King and Country" debate in the Oxford Union, and later Attorney General and judge in Sarawak.Digby was educated at Quernmore School, Bromley, and undertook his medical studies at Guy's Hospital, London, where he was a prize-winning student (holding the Michael Harris, Hilton and Beaney Prizes) and where he gained his MB, BS in 1907 and became a Fellow of the Royal College of Surgeons in 1910.