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The English actor, in his interview with HitFix, explains that his role as MI6 agent Bill Haydon is the opposite of Gary Oldman's George Smiley in a lot of ways.
"Haydon is a fantasist. He wants to be seen," Firth said. "He's the one who flirts outrageously. He wears red socks."
The commentary on details like socks is part of the "complex stuff" of the movie. It is Smiley's charge to uncover who in MI6's upper ranks is doubling as a mole for the Soviets, during this tale of espionage and the Cold War. Firth is among the "suspects," each character giving out in drips and drabs of the "odd gesture and odd line."
Firth's oddness, he said, is informed by "Lawrence of Arabia," that Haydon would be the type to "lead people into battle on a camel.
Check out the "King's Speech" actor's take on the helpfulness of John le Carre's original "Tinker Tailor" novel and more in the video above.