[6][7][8] His paternal grandparents were the Oxford academic and journalist William Leonard Courtney and his first wife, Cordelia (née Place).

He performed national service in the British Army, leaving after 18 months as a private, not wanting to pursue a military career.

He made guest appearances in several cult television series, including The Avengers (1962, 1967), The Champions (1968), Randall and Hopkirk (1969) and as a racing driver in Riviera Police (1965), and briefly appeared as a TV panel chairman in the film Take a Girl Like You (1970), hosting a debate between John Bird and John Fortune.

Camfield kept Courtney in mind for future roles, and later that year cast him in The Daleks' Master Plan, in which he played Space Security Agent Bret Vyon.

[15] The Lethbridge-Stewart character returned in the next season in The Invasion, promoted to the rank of brigadier,[3] and in charge of the British contingent of UNIT.

Years later, actor and writer Ian Marter (who played UNIT medical officer Harry Sullivan alongside Tom Baker) named a Russian military base used in The Invasion, but unnamed on screen, "Nykortny" in his novelisation of the story.

Courtney made his final appearance in the 1989 serial Battlefield (although like many other former cast members, he reprised the role for the charity special Dimensions in Time).

in 1977, where he appeared again with Jon Pertwee, Minder (1984), All Creatures Great and Small (1980, episode "Matters of Life And Death"), Only Fools and Horses (1988) and Yes, Prime Minister (1986), and the 1984 television movie To Catch a King.

Courtney also appeared in the Big Finish Productions audio drama Earthsearch Mindwarp, based on a James Follett novel, broadcast on the digital radio station BBC 7.

Courtney starred as Inspector Lionheart opposite fellow Doctor Who actor Terry Molloy in the audio series The Scarifyers, from Cosmic Hobo Productions.

The first two Scarifyers adventures, The Nazad Conspiracy and The Devil of Denge Marsh, were broadcast on BBC 7 in 2007; the third, entitled For King and Country in 2008, and fourth, The Curse of the Black Comet, in 2010.

[2] Doctor Who audio play producers Big Finish, with whom Courtney had worked on several releases in his continuing role as the Brigadier, confirmed the date of his death as 22 February 2011.

Baker wrote "We shall miss him terribly" in a newsletter on his website, in which he also indicated that Courtney had been battling cancer for a few months prior to his death.