Trivia

Samuel West, who portrays Anthony Blunt in this series, played the same role 16 years later in season 3, episode 1 of The Crown (2016).

This mini-series' writer Peter Moffat said of this production: "This is the story of four young but devastatingly effective double-agents who knew from the start that they stood or fell together. Burgess is the loudest spy in the history of espionage, a gifted gob and wicked wit. Philby is the most successful spy of the lot, becoming Head of Counter-Intelligence in MI6. Blunt is cool, viciously funny and clever, while Maclean veers between being warm and friendly and drunk and difficult. Until Burgess and Maclean's desperate flight to Moscow on 23 June 1951 they live in each other's pockets.""

Based on the same real life events as Another Country (1984), History in Faces: Cambridge Five (2011), Philby, Burgess and Maclean (1977), A Question of Attribution (1991), An Englishman Abroad (1983), Tinker Tailor Soldier Spy (2011), Tinker Tailor Soldier Spy (1979), Blunt (1987), Traitor (1971), Blade on the Feather (1980), The Jigsaw Man (1983) and influenced the source novels of The Fourth Protocol (1987), The Innocent (1993) and others works such as A Different Loyalty (2004) and Olding (2019), even in minor form like in The Imitation Game (2014).

Actor Tom Hollander has appeared in such espionage movies as Hanna (2011), Enigma (2001), and Mission: Impossible - Rogue Nation (2015), as well as the later BBC television spy series, The Night Manager (2016), an adaptation of a John le Carré 1993 novel of the same name.

Actor Benedict Cumberbatch, who plays Edward Hand in one episode, would later star in The Imitation Game (2014).