Born in 1884 at Boston, Lincolnshire son of William Gilliatt, he received his medical training at the Middlesex hospital, where he was an outstanding student. He won the Hetley clinical scholarship, the junior Broderip scholarship, the Leopold Hudson scholarship and the Lyell gold medal and scholars

Born at East Hoathly, Sussex on 18 September 1884, where his father and grandfather had practised, he was educated at Eastbourne College and Gonville and Caius College, Cambridge. There he took second class honours in the Natural Sciences Tripos part I in 1905, and following the family tradition did