A mole, implanted by Moscow Centre, has infiltrated the highest ranks of the British Intelligence Service, almost destroying it in the process. And so former spymaster George Smiley has been brought out of retirement in order to hunt down the traitor at the very heart of the Circus – even though it may be one of those closest to him.
An unarguable classic which at the time pushed the boundaries of television technique. The sheer physical darkness of the footage terrified the executives supervising production, but the end result is definitive TV, with echoes in The Wire and True Detective. Sir Alec Guinness is iconic as Smiley.