This television movie tells the true story of the "Cambridge spies", but there was something that the filmmakers did not know when it was made. There was a fourth Cambridge spy, the art historian Sir Anthony Blunt, who was publicly exposed two years after this movie was first televised.
In this drama Anthony Bate plays the traitor Kim Philby. In Tinker Tailor Soldier Spy (1979) he plays the senior civil servant who brings George Smiley (Alec Guinness) out of retirement to hunt out the fictional mole who was based in part on Philby.
Based on the same real life events as Another Country (1984), Cambridge Spies (2003), History in Faces: Cambridge Five (2011), 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).