First broadcast 24th September 1979.

'It's the oldest question of all, George: who can spy on the spies? You'll take the job? - do whatever is necessary?'
And so, George Smiley sets out for Oxford to visit an old and invaluable friend and Peter Guillam is despatched to play Burglar Bill.

George Smiley: Alec Guinness
Peter Guillam: Michael Jayston
Lacon: Anthony Bate
Bill Haydon: Ian Richardson
Roy Bland: Terence Rigby
Toby Esterhase: Bernard Hepton
Connie Sachs: Beryl Reid
Control: Alexander Knox
Percy Alleline: Michael Aldridge
Bryant: Frank Compton
Lauder Strickland: Frank Moorey
Senior secretary: Jean Rimmer