 Bull was educated at Winchester College.His first professional stage appearance was in "If I Were You" at the Shaftesbury Theatre in 1933.He was a friend of Alec Guinness, whom he first met at HMS "Raleigh" during training in World War II, and later HMS "King Alfred"; he served as an officer in the Royal Naval Volunteer Reserve, later commanding Landing Craft (Flak) 16 in the Mediterranean.