Shortly before filming began, Alec Guinness asked author John le Carré to introduce him to a real spy to aid him in preparing for his role. Le Carré invited him to dinner with Sir Maurice Oldfield, who served as Chief of the British Intelligence Service from 1973-78. During their meal Guinness studied Sir Oldfield intently, noting any mannerisms/quirks he could use in his performance; when he saw Oldfield run his finger around the rim of his wineglass, and asked whether he was checking for poison, to Oldfield's astonishment as he was only checking how clean the glass was.
Alec Guinness was very concerned that he wasn't the right type to portray the "frog-like" George Smiley. Three weeks into filming, Alec Guinness panicked and asked to be replaced, and recommended Arthur Lowe for the role of Smiley. However, he eventually overcome his doubts and went on to receive critical acclaim for his role.
The code name for the British Intelligence secret service was "The Circus". John le Carré told the producer that the BBC offices matched his image of the Circus, and so parts of the Circus office interiors were filmed in the offices of the BBC.
During production, Alec Guinness complained that George Smiley's characteristic habit, polishing his glasses with the fat end of his tie, could not be done naturally because London's cold weather resulted in Smiley wearing three-piece suits. Thus a handkerchief was used as a substitute. John le Carré's sequel novel 'Smiley's People', mentioned a statement referring to this issue: "From long habit, Smiley had taken off his spectacles and was absently polishing them on the fat end of his tie, even though he had to delve for it among the folds of his tweed coat."
Alec Guinness loosely based George Smiley's look and behaviour on Sir Maurice Oldfield, a former head of British intelligence. John le Carré also claims that Alec Guinness "stole his hairstyle" for George Smiley.
John le Carré has admitted that the vocabulary used in the novels/series (babysitters, lamplighters, the Circus, the nursery, moles) was made up. He was later amused to discover that real agents had begun to appropriate some of his vocabulary once his espionage stories were published.
Source author John le Carré included 'Tinker, Tailor, Soldier, Spy' as one of his four best novels during an interview on 5 October 2008 on BBC Four. The other best works he selected were 'The Spy Who Came in from the Cold', 'The Tailor of Panama' and 'The Constant Gardener'.
The series's initial broadcast coincided with the UK Government announcing that Anthony Blunt, the Keeper of the Queen's Pictures, was one of the Cambridge Five (a ring of spies in the UK who passed information to the Soviet Union during/post-World War II).
In the United States, syndicated broadcasts compressed the seven British episodes into six (also the current U.S. DVD version), thus scenes were shortened and the narrative sequence altered. In the British version, George Smiley visits Connie Sachs before Peter Guillam's burglary at the Circus, while the U.S. version reverses the sequence of these events.
In the United States, the PBS network broadcast the series as a Great Performances (1971) programme introduced by the Canadian journalist Robert MacNeil, who explained the workings of the British Secret Service.
John le Carré once paid an unexpected visit to the set during filming. Alec Guinness stopped acting immediately and asked that le Carré leave so he could continue. Guinness later maintained that it was disconcerting performing with le Carré watching, as he had based a lot of Smiley's performance on the writer himself.
The 1974 'Tinker, Tailor, Soldier, Spy' novel is the first book in John le Carré's Karla or Quest for Karla Trilogy, the second and third parts being 'The Honourable Schoolboy' (1977) and 'Smiley's People' (1979).
Writer John le Carré partially based his famous George Smiley character on a friend, the Lincoln College tutor and Oxford University don, the Reverend Vivian Green. Smiley was also based on le Carré's boss at Mi5, Lord Clanmorris, who wrote crime novels under the pseudonym of John Bingham.