John Edwin Arnatt was born on the eve of the Russian Revolution in Petrograd, Russia, to a manager for Vauxhall Motors, and was forced to leave the country during the turmoil. His family subsequently returned to England, where he was schooled at Epworth College and later trained for acting at the Royal Academy of Dramatic Art (RADA).
Arnatt began his stage career in 1936 and made his West End debut in 1938 in the revue "Happy Returns." He continued to perform on stage throughout the 1940s, including wartime army service, and even had a brief stint as a stand-up comic at the Windmill Theatre.
In the 1950s, Arnatt appeared in plays by Shakespeare and Chekhov at the Arts Theatre Club and the Old Vic, both in London and Bristol. He also worked as a sports reporter on commercial television under the pseudonym "Howard Peters."
Arnatt was a tall man with urbane manners, a no-nonsense attitude, and often sported a pencil moustache. He is best remembered for his many impersonations on screen of thoughtful, pipe-smoking authority figures, including Scotland Yard inspectors, commissioners, diplomats, aristocrats, and army officers.
One of his most notable roles was as the Time Lord Borusa, one-time Lord Chancellor of Gallifrey, in the 1963 Doctor Who serial "The Invasion of Time." He also played the deputy sheriff in The Adventures of Robin Hood (1955),serving as a worthy antagonist to Richard Greene.