The actor takes the role of espionage specialist George Smiley in the film adaptation of the novel by John Le Carre, but insists fans of Matt Damon's 'Bourne' movies and those featuring the iconic British spy may be disappointed when they watch his movie.
He said: "It is the polar opposite of Bond and it is not 'The Bourne Identity'. It is an intellectual thriller. You have to focus and listen."
Comparing the new adaptation to a BBC TV series made in 1979, Gary promised his version is "sexier" and ore gritty.
He explained: "It is not such a cosy English affair and it is a bit sexier than before. The television series is 30 years ago and it was somewhat nostalgic then.
"The Cold War was close and of course you were closer to the 'commie-watchers' and all of that, which now is in the mists of time."
Gary also says the character of George has been updated from being "a rather short guy, unattractive, overweight" for his part, which he described as a "wonderful role" to play.
He added: "It's a delicious part, a wonderful role. Smiley is middle-aged, mild-mannered, sagacious and perspicacious.
"He is an intelligence officer, a student of espionage. He has a strong moral sense, too, a strong moral compass, even though he recognises the dark, unethical, ugly side of what he does. Also, there's a melancholy and sadness within George. It isn't accidental that his name is Smiley."