Doctor Who
Director Douglas Camfield originally considered Courtney for the role of Richard the Lionheart in The Crusade (1965), a role that ultimately went to Julian Glover. Though Camfield made sure to keep Courtney in mind for future casting. Courtney would make his first appearance in the series, when Camfield cast him in the 1965 serial The Daleks' Master Plan, where he played Space Security Agent Bret Vyon opposite William Hartnell as the Doctor.
Camfield liked Courtney's performance, and when the director was assigned the 1968 serial The Web of Fear, he cast Courtney as Captain Knight. However, when David Langton gave up the role of Colonel Lethbridge-Stewart to work elsewhere, Camfield recast Captain Knight and gave the part to Courtney instead. The Lethbridge-Stewart character returned in the next season in The Invasion, promoted to the rank of Brigadier and in charge of British contingent of UNIT. The organisation had been charged with protecting the Earth from alien invasion.
It was in this recurring role that he would become best known the viewing audience, appearing semi-regularly in 101 episodes between 1970 to 1975. The character proved popular enough to return in 1983, first in Mawdryn Undead and in the official 20th anniversary special The Five Doctors. 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). He appeared with Jean Marsh in both his first and last regular Doctor Who television appearances. Jean Marsh portrayed the character of Sara Kingdom in Courtney's first appearance, The Daleks' Master Plan, playing his character's sister. In Courtney's final appearance on the show, Marsh portrayed the villainous Morgaine in the Arthurian inspired Battlefield.
Courtney has played Lethbridge-Stewart, either on television or in audio plays, alongside every subsequent Doctor up to and including Paul McGann, as well as substitute First Doctor Richard Hurndall. He did not appear in the revived series. While he has acted with Tenth Doctor actor David Tennant in the Big Finish audio dramas Sympathy for the Devil and UNIT: The Wasting, Tennant was playing a different character, Colonel Ross Brimmicombe-Wood, on both occasions. In 2000 he got back in uniform to recreate the character of Brigadier Lethbridge-Stewart for a couple of sketches in the third season of The Harry Hill Show.
The character is referenced in the Series 4 episode "The Poison Sky" and is said to be "stuck in Peru". Fifteen years after Dimensions in Time, Courtney returned as Lethbridge-Stewart (now, Sir Alistair), freshly returned from Peru, in "Enemy of the Bane", a two-part story in the Doctor Who spin-off The Sarah Jane Adventures aired in December 2008, starring Elisabeth Sladen as Sarah Jane Smith. The Sarah Jane Adventures production team intended that Courtney would reappear in the following year's The Wedding of Sarah Jane Smith so that Lethbridge-Stewart would meet the Tenth Doctor, but Courtney was recovering from a stroke and unable to take part.
In the Doctor Who episode "The Wedding of River Song" it is stated that Brigadier Lethbridge Stewart had died.
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