He appeared in more than one hundred television dramas on the BBC and ITV during the course of his career, including Our Friends in the North, Poldark and House of Cards.

[1] He served in the British Army during World War II, making his stage debut in Dangerous Corner at Preston, Lancashire, for the forces' entertainment organisation ENSA.

[1] In 1948 he enrolled at the Central School of Speech and Drama, receiving commendation for his student performance in Mary Hayley Bell's Men in Shadow.

His first professional West End appearance was in 1959, in William Douglas-Home's Aunt Edwina, followed by his creation of the hit-man Ben in the London premiere of Harold Pinter's The Dumb Waiter at the Hampstead Theatre Club in January 1960.

In 1963 Selby made his first appearances for the Royal Shakespeare Company, as Casca in Julius Caesar, the Bishop of Winchester in The Wars of The Roses and Antonio in The Tempest.