Michael Fassbender is leaning against the wall of an East London office block, having a crafty smoke. He is strikingly handsome; blue eyes, killer cheekbones, red stubble.

The last time I saw him with fag in hand was in Hunger, the Bafta-winning portrait of the Irish hunger-striker Bobby Sands that made him one of the most sought-after actors on both sides of the Atlantic. His smoking then (like his acting) was scarily intense; he knew that in the Maze prison, “cigarettes were like f***ing gold dust”. Now, with the 14kg weight loss, the scenes of smeared excrement and the bed sores behind him, Fassbender, 31, is puffing away, carefree, like a man with a part in the new Quentin Tarantino movie.

Hunger, he says, as we slip into a nearby café, has “changed things hugely. Now I can get into rooms early when projects are starting up”. In recent months he has been mentioned as Heathcliffe in a new film of Wuthering Heights and in the Dennis Waterman role, opposite Ray Winstone, in a movie version of The Sweeney. But the most exciting is Inglourious Basterds (sic), Tarantino’s Second World War tale of a suicide squad sent to kill as many Nazis as they can.

Filming ended in December and Fassbender had a blast playing a British commando who teams up with Brad Pitt’s homicidal Yanks. His character, Lt Archie Hicox, was based, Tarantino told him, on a young George Sanders. “So I got out all the original Saints and Sanders films. It’s a very particular way of speaking, affected accent and mannerisms. I just really went to town and found quite a lot of humour in it, I hope.” Pitt certainly thought so. “In our first scene together I started doing my character and he started laughing.” He smiles. “He was very supportive.”

His languid affability seems so at odds with the asceticism of Hunger. This son of a German father and an Irish mother is an usual mix of monk and monkey. “I suppose the German side wants to keep everything in control and the Irish side wants to wreak havoc!” he grins. Born in Heidelberg, he moved to Killarney at the age of 2. He was teased about his name: “You can imagine the combinations you can make with a word like Fassbender.” But Germany and Ireland actually have a history of goodwill, he insists. “Somebody told me — this could be wrong, but never let the truth get in the way of a good story — that the German football team’s away strip was green because Ireland were the first to play them after the war.”

His father, a chef, ran a restaurant in Killarney with his Northern Irish mother, who thinks she may be a relation of the 1920s Irish revolutionary leader Michael Collins. He has an elder sister who lives in California, which is also where his girlfriend lives. She is involved in the business, “but I’d better leave it there.” He admits that he has never felt truly Irish or German. So, after training at the Drama Centre in London, cracking the UK acting world, with its obsession with received pronunciation, was tough. But he has made his ambiguity work for him, using an impressive array of accents.

The plummy tones of Inglourious Basterds contrast with his American twang in Band of Brothers (his big break), the Northern Irish lilt of Hunger and his curious, quasi-Dutch effort in the British “hoodie horror” Eden Lake. “Actually, it’s just my own accent that I used in Eden Lake,” he says. It’s not the one you’re talking in now, I say, which is unmistakably Irish. “Really?” he says. “I don’t know, it’s so f***ed up. Whenever I go home I get the piss taken out of me.”

Fassbender’s laidback fatalism seems very Irish, as does his creative storytelling. Growing up, his dad, with his cooking, was the artistic one, but it was his mum, who took care of front-of-house at their restaurant, who fostered an interest in cinema. A favourite was the German director Werner Fassbinder, who, as the spelling suggests, is no relation, “although he has become a relation in certain interviews — and auditions!” So it’s Fassbinder on one side, and Michael Collins on the other? “Yeah, and we’re not 100 per cent sure on the Michael Collins thing either!”

Next up, he is returning to the territory of 300, in which he played a Spartan warrior, with another revisionist historical epic, Neil Marshall’s Centurion. On the way back from the Basterds shoot in Berlin, he bumped into an amateur historian. “I said I was doing this film about the ninth legion in the Highlands of Scotland and how they got wiped out. He said, ‘Yeah, that’s bullshit. They were nowhere near Scotland.’ But it hasn’t put me off.” Never let the facts get in the way of a good story, right? “Absolutely!” he chuckles.

Hunger is out now on DVD; Inglourious Basterds will be released in the summer

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