He was the son of Hammersmith MP Sir William James Bull, 1st Bt..

Bull was educated at Winchester College. His first professional stage appearance was in If I Were You at the Shaftesbury Theatre in 1933.

Bull's performance as the Russian Ambassador, Alexi de Sadesky, in Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb (1964) is among the best-known of his several dozen film and TV appearances. He both narrated and had a small on-screen role in Scrooge (1951), and portrayed the German ship's captain in The African Queen (1951).

Bull was also the first ever actor to portray Pozzo in the English-language version of Beckett's 'Waiting For Godot' when it opened on 3 August 1955.

In the 1970s he ran a small shop just off Notting Hill Gate, selling zodiac-related items.

Bull wrote a work on the subject of teddy bears, Bear With Me. He also wrote a non-fiction work about his experiences during World War II as commander of a Tank Landing Craft (LCT), To Sea in a Sieve. During his service, he achieved the rank of Lieutenant-Commander and was awarded the DSC.