Benedict Cumberbatch likes his suit.

It’s a natty, beige three-piece, which is offset with a white shirt and crisp blue tie. It not his own, however. It belongs to his character, and therefore to the prop department, but such is his sartorial interest, he knows its lineage. “It is Timothy Everest, on Elder Street in Shoreditch,” he begins, running his finger along the lapel. “It’s a world-famous, bespoke tailor that isn’t on Savile Row. My character is one of the sharper dressers in the film.”

The film in which he is so sharply dressed is Tinker, Tailor, Soldier, Spy, the first-ever big-screen adaptation of John le Carré’s most famous novel. It is a Cold War thriller brimming with illustrious talent – Gary Oldman as the iconic spy George Smiley is joined by the likes of John Hurt, Kathy Burke, Colin Firth and Toby Jones – with Cumberbatch standing alongside Tom Hardy and Stephen Graham as one of the movie’s Young Turks.

The 35-year-old actor became a household name on the back of his leading performance in last year’s Sherlock for the BBC, and he’s made the most of his moment, securing parts in Steven Spielberg’s forthcoming adaptation of Michael Morpurgo’s novel War Horse, Peter Jackson’s two-part rendition of The Hobbit, and in Tinker, Tailor, Soldier, Spy.

“Tinker, Tailor was a creative offer before it was a financial one,” he says with a smile, “because they wanted famous people in all the roles and Sherlock hadn’t come out. Once that was out, it suddenly became a commercial offer as well.”

The le Carré piece opens in cinemas next week, Cumberbatch taking on the role of Peter Guillam, a member of the Intelligence Service who Smiley takes under his wing as he bids to unearth a mole buried deep within British ranks. He’s an important character, who shares much screen time with Oldman’s Smiley, and the actor is grateful for the opportunity.

It almost wasn’t so. Director Tomas Alfredson, who made his international breakthrough with 2008’s vampire movie Let The Right One In, identified Cumberbatch early on, although the actor was preparing and previewing a forthcoming play, Terrence Rattigan’s neglected After The Dance, for the National Theatre.

“I’d heard that the director wanted to meet,” he says, temporarily encamped inside a trailer parked on set at a disused Army barracks in Mill Hill, North London, “but I said that because of the theatre previews I would not have time to read the script. Everyone said that was fine and that they’d get a message to him.”

Cumberbatch arrived at the office of Working Title, the British film producers funding the project. Alfredson greeted him warmly. “Then the first thing that Tomas said to me was: ‘What did you think of the script?’ I told him I hadn’t read it and he just looked at me, mouth agape: ‘You, you, you haven’t read the script?’ I felt awful. He was sat at this glass table at the top floor of these new offices, and there’s this massive mural by Gilbert & George on the wall, a status bit of artwork, with its really bright colours showing the modern social malaise. It was all a little odd.” Fortunately, Cumberbatch charmed his director, went away, read the script, and also wrote Alfredson an email explaining why “the meeting had been a real f*** up”.

Guillam proves one of the story’s less opaque characters. “Guillam has a very clear morality,” says Cumberbatch. “He sees what he is fighting for as the right and good cause and, in a way, he wants to be part of something heroic, like the Hot War, where the lines were very clearly delineated and undivided.”

Unfortunately for Guillam he’s very much embroiled in the Cold War, a world of “lamplighters”, “shoemakers” and “pavement artists”, as imagined by le Carré in the service that he dubs The Circus. He is himself a former Secret Agent and serves as an executive producer on the movie, championing its production in the face of criticisms that it will never outshine the BBC serial, which ran in 1979, with Alec Guinness conjuring a memorable performance as Smiley.

Cumberbatch’s dedication comes through as he rattles off his character’s back story: “Before this story begins Guillam’s a man who ran an operation in North Africa ... Morocco probably.” He pauses, briefly. “A port town, where he was a clerk and he had Arab agents. Being a French Protectorate, he is fluent; he is Anglo-French, his father was French and worked in the Resistance and his mother, we think, worked in Bletchley Park.”

None of this information is vital to the audience’s understanding of the man on screen, but it is important to Cumberbatch. He wants to repay the filmmakers’ trust. “I’m framing my call-sheet from yesterday because it was Colin Firth, Kathy Burke, Stephen Graham, Gary Oldman, John Hurt – even John le Carré made a brief appearance. He was on this call-sheet, and I got him to sign mine. It really was an extraordinary day at work.”

The actor’s extraordinary days have spread beyond Tinker, Tailor. In January next year he’ll appear in War Horse, playing Major Stewart, and he’ll follow that with a delectable role in the two-film adaptation of The Hobbit, where he’ll voice the unsavoury duo of Smaug the dragon and Sauron the arch necromancer.

Earlier this year, he also teamed up with Danny Boyle for his version of Frankenstein at the National Theatre. “Danny started in the theatre,” says Cumberbatch. “He directed Gary Oldman in The Pope’s Wedding, with Max Stafford-Clark, so to be working with people like Gary and Danny is just incredible.”

Cumberbatch has worked consistently in theatre since graduating from LAMDA, earning an Olivier nomination for Best Performance in a Supporting Role for his role in 2005’s Hedda Gabler. He was born in London, an only child, to actor parents Timothy Carlton and Wanda Ventham, and granted an expensive education at Brambletye and Harrow Schools, growing up in what he concedes was “an incredibly privileged bubble”. He is currently single, having split from his partner of 12 years, actress Olivia Poulet, last year.

Following a string of successful theatre performances he enjoyed success on television for the BBC in the likes of Hawking (2004), the miniseries The Last Enemy (2008), and Small Island (2009). His film credits, meanwhile, encompass the historical drama Amazing Grace (2006), the Second World War romance Atonement (2007) and the Darwin movie Creation (2009). He’s also shot The Whistleblower, a thriller with Rachel Weisz.

Film is where he sees his immediate future, and he recently declined the chance to reprise his critically lauded role in After The Dance. “It does seem as though I have a bit of momentum at the moment,” he says, “and while I love theatre it is always a huge commitment and I’d like to keep myself available for more film work.”

He says he’s watched with envious eyes as fellow thirtysomethings – such as James McAvoy, Michael Fassbender and Ben Whishaw – have all worked their way “to the big table”. He says that he now wants “a little taste of that” and if his studied, highly nuanced performance in Tinker, Tailor is a taste of what’s to come, Cumberbatch will surely be dining at the top table for a while yet. He’ll no doubt wear a natty suit, to boot.

Tinker, Tailor, Soldier, Spy opens on Friday