This dramatisation of John Le Carré's novel proved a landmark in British television. It received supreme critical acclaim for the screenplay by Arthur Hopcraft, the star Alex Guinness and the camerawork of Tony Pierce-Roberts.

In Alex Guinness's first major TV role he plays George Smiley, a retired agent who is secretly brought into "the Circus" (the code name for British Secret Intelligent Service) to root out a top-level mole. Gradually piecing together the story, the weary but determined Smiley trawls through the murky waters of Cold War espionage and his own past.