Terrence Hardiman (born 6 April 1937) is an English actor. He is best known for playing The Demon Headmaster in the children's television series of the same name, and also for Reinhardt in the 1970s drama series Secret Army.
He also had a starring role as Charles Pooter in the 1979 television adaptation of George and Weedon Grossmith's Diary of a Nobody, a role which shows his versatility more than the succession of officers he usually portrays. Hardiman's other recurring role was as Brother Cadfael's boss, Abbot Radulfus, in the television series. Joining him throughout the series as Prior Robert was Michael Culver, who had played his predecessor Major Brandt in Secret Army. A notable small role Hardiman played was a version of the Sergeant Wilson character from Dad's Army in an episode of time travel comedy Goodnight Sweetheart, called "Don't Get Around Much Any More", in which Nicholas Lyndhurst's character Gary Sparrow goes back in time to a 1940s bank and encounters characters called Mainwaring and Wilson. Hardiman's portrayal was a keenly observed impersonation of John Le Mesurier's own performance, incorporating many of the tics and mannerisms of the original. Hardiman also appeared as Chief Wizard Egbert Hellibore in four episodes of The Worst Witch. Hardiman appeared in the second series of The Worst Week of My Life. Another notable recent role was as a devious Swiss murder victim in an episode of crime mystery series Jonathan Creek. He has also appeared in the daily BBC1 soap Doctors on 3 April 2009 and 14 &15 January 2015 and in the Yorkshire drama Heartbeat as John Upton in one episode. In 2009 he appeared in a 3D film for the BFI called Radio Mania directed by British artists Iain Forsyth and Jane Pollard. Hardiman appeared as Hawthorne in the Doctor Who episode The Beast Below on 10 April 2010.