In the novel, Jim Prideaux's mission took place in Czechoslovakia. In the film, the mission takes place in Hungary. The change in location was because Hungary offers a twenty percent tax reduction for film productions.
Gary Oldman went to Old Focals, an eyeglass store in Pasadena, to search for the right glasses to fit George Smiley: "Glasses are funny things. For Smiley, they're iconic. It's like Bond's Aston Martin or vodka martini." Oldman tried on hundreds of glasses frames before he found the appropriate spectacles.
Tomas Alfredson based the environment on his first impressions of London when he first visited the town in the 1970s: a brown and gray palette, shadows and uncovered light-bulbs, and dirty streets. "If you see London now and at that time, it's two different cities. Today it's a white city; then it was black; it was so dirty, and you could still feel the War all around."
To prepare for the role of George Smiley, Gary Oldman ate a lot of treacle sponge and custard to "put on a bit of middle-aged tummy". Oldman also watched Sir Alec Guinness' performance in Tinker Tailor Soldier Spy (1979), and paid a visit to Smiley's Creator John le Carré: "The way he touched his shirt, spoke and so on, I took all that and used it. I hope he won't mind, but Smiley is in his DNA."
Tomas Alfredson had John le Carré write part of the dialogue for the Circus conference: "When we rehearsed it, it felt as if Bill Haydon should say something, but what would he say? Well, why not call John le Carré and see if he's in? And we called him and we described the situation. He thought for fifteen seconds and he said, grab a pen, here it is! It was a fantastic moment." Colin Firth jokingly suggested a velvet cushion for the paper on which the line was written.
In one of the flashback scenes, Control (Sir John Hurt) is speaking on the phone, on the desk behind him are two bulldogs draped in the Union Jack. These figurines were created by Royal Doulton during World War II to represent Patriotism. In Skyfall (2012), M (Dame Judi Dench), the head of MI6, has the same Royal Doulton bulldog on her desk.
John le Carré's novel was based on the uncovering, during the 1950s and 1960s, of the Cambridge Five traitors, who were K.G.B. moles working within the S.I.S. It is the first book in le Carré's Karla, or Quest for Karla trilogy, the second and third parts being The Honourable Schoolboy (1977) and Smiley's People (1979).
George Smiley first appears seven minutes into the film, and although he appears repeatedly in the following minutes, he does not speak his first line until eighteen minutes into the film. That line is, "I'm retired now, Oliver, you fired me."
Gary Oldman described Tomas Alfredson as taking a near-voyeuristic approach, by shooting with long lenses: "It was as if he was eavesdropping, like a peeping Tom, which is what you sort of want for a spy film."
To prepare for his role as Peter Guillam, Benedict Cumberbatch went to the Moroccan town of Essaouira, where Guillam had been stationed in the story: "It's got a slightly nightmare quality. I was wandering around the streets at night, thinking what it must be like to know that every turn could be my last."
The filmmakers consider this film's version of George Smiley as the most emotional one yet: "You see a wilder person inside Gary's eyes. He can probably be crueler, maybe even more melancholic. He's a man presenting himself one way, yet internally, there's a great sadness."
Gary Oldman based his performance as George Smiley on a line from the novel: "George is like a swift, Ann once told Haydon in George's hearing. He lowers his temperature until it's the same as the room around it. Then he doesn't lose heat by adjusting." Tomas Alfredson further compared Smiley to a turtle, "because the turtle has so much of its body hidden inside a shell; it is fixed, and it doesn't have a lot of different expressions."
As this movie is about the uncovering of an infiltrator into the British Secret Service, and Director Tomas Alfredson's previous film was called Let the Right One In (2008), this film was jokingly referred to as "Get the Wrong One Out".
The Swedish song heard in Control's first scene is "Land, du välsignade" (Blessed Country) sung by Jussi Björling. Tomas Alfredson is Swedish. However, the song also serves as an indication of Control's patriotism.
John le Carré included "Tinker, Tailor, Soldier, Spy" as one of his four best novels during an interview on October 5, 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".
When Jim Prideaux (Mark Strong) spots George Smiley at the school, he asks Bill Roach if it's a beggar man or a thief. "Beggar man, thief" is the ending part of the children's rhyme, upon which the movie's and novel's title is based. Additionally, as mentioned in the novel (but not in the film), "Beggar man" is Smiley's code name in the "Tinker, Tailor" sequence.
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.
This second adaptation was released thirty-two years after the renowned television series Tinker Tailor Soldier Spy (1979), just under thirty years after its sequel Smiley's People (1982), and thirty-seven years after the novel was published.
Second filmed adaptation of a John le Carré novel to have a score composed by Alberto Iglesias. His first was for The Constant Gardener (2005). Both music scores were Oscar nominated in the Best Music Score category, for the Academy Award for Best Achievement in Music Written for Motion Pictures, Original Score.
Filming took place at a disused Army barracks in North London, a location much cheaper and affording wider space for the set designers than renting buildings in London for filming. The barrack's corridors and alcoves were used for interior shots, and the side of a building was dressed up as a Wimpy bar.
The letters addressed to George Smiley's wife, Lady Ann, show the address as 18 Asherton Street, Islington, N1. In the books, Smiley famously lived off the Kings Road, at (No 9) Bywater Street, Chelsea, SW3.
At one point, the song "Mr Wu's A Window Cleaner Now" is played on the radio and sung along by several characters. This song was originally from To Hell with Hitler (1940), in which George Formby played a ukulele player, mistaken for a spy.
As Peter Guillam, Benedict Cumberbatch recited a few lines from the poem "Casabianca". Three years earlier, in the radio comedy Cabin Pressure, his character was mocked with a few lines from the same poem.
The trivia items below may give away important plot points.
To prepare for his role as Bill Haydon, Colin Firth reviewed footage of Kim Philby's 1955 press conference. In this conference, held after the defection of the British traitors Donald MacLean and Guy Burgess, Philby vehemently denied that he was a traitor. Seven years later, he fled to Moscow. "You can see the tremendous tension in his body language, and in his facial expression, but he cannot hide the sense of mischief."
In the novel, Peter Guillam was in a relationship with a female musician named Camilla. In the film, he is a homosexual in a relationship with a man, according to Benedict Cumberbatch, a creative decision that works well within the film: "Sexuality was a very powerful tool then. Guillam keeps his homosexuality secret, because he is so open to blackmail. It necessitates a certain amount of secretiveness, which goes hand in hand with spying."
The French song heard in the film's closing scenes is "La Mer", sung by Julio Iglesias. This song was chosen by the filmmakers because they thought it was a song George Smiley would listen to when he was alone. Tomas Alfredson described the song as "everything the world of MI6 isn't."
The chess pieces Control uses in the film are: Karla as a white queen; Alleline (Tinker) as a white rook; Haydon (Tailor) as a white bishop; Bland (Soldier) as a black king; Esterhase (Poorman) as a black knight; and Smiley (Beggarman) as a black queen. Later on, Smiley uses Polyakov as a black bishop. Using the same piece for Smiley and Karla hints at their mastermind status and rivalry (the queen is the most powerful piece in chess); using the same piece for Haydon and Polyakov hints at their connection.