Born in Ilford, Essex, on December 10, 1941, Campbell studied drama at RADA before touring in rep. But in the early Seventies he set up is own theatre group, named after himself, that performed in unusual venues such as pubs. Members included Bob Hoskins and Sylvester McCoy.

In 1976, he and Chris Langham formed the Science Fiction Theatre of Liverpool to stage Illuminatus!, an eight-and-a-half hour cycle of five of his own plays, as well as an unsuccessful stage adaptation of The Hitchhiker's Guide to the Galaxy, with Langham as Arthur Dent.

Campbell’s TV credits include Alf Garnett's neighbour in In Sickness And In Health, and the irritating Roger in an episode of Fawlty Towers. On radio he played Poodoo in The Hitchhiker's Guide and he unsuccessfully auditioned for the part of the seventh Doctor Who in 1987, being beaten to the role by Sylvester McCoy.

Campbell has more recently been known for his series of one-man shows, the most successful of which has been The History of Comedy Part One: Ventriloquism.