The handshake is firm, the greeting is garrulous and the electric blue eyes are fixed firmly on mine. Marc Warren, the body language screams, is a man who, like his conman in Hustle, spits in the face of insecurity.

Not if I had seen him a minute ago, he insists in his Estuary chirp. “I was in the loo and I just said to myself, 'Come on!' I get nervous talking about myself but I need to keep my eyes on the prize, to sell this show because I really believe in it.”

The show is Mutual Friends, a marvellously turbulent comedy drama in which Warren, 42, stars as Martin, a corporate drone who discovers that his dead best mate had slept with his wife (Keeley Hawes). The role brought his flaws to the surface: “It f***** me mentally, because I was playing someone who was stressed, anal, emotionally inept, constantly shouting.”

Unlike Martin, Warren - absurdly youthful in shorts and T-shirt, his hair boyish blond, his face barely lined - opens up to his male friends: “I'm always telling them I love them”. But he did find himself mimicking his character's neuroses, constantly checking doors were shut and cars locked: “It drove me scatty. If you spend all your time doing something, it bleeds into your life.”

He has history here. On the set of the gruesome crime series Messiah he was monosyllabic; in Hustle he was a picture of affability. “We all wear so many hats, don't we?” he says.

Some wear more than others. It has been Warren's willingness to veer in unexpected directions that has marked him out from his equally photogenic peers.

There was the Byronic vampire in Granada's Dracula, the shady goverment fixer in Burn Up and the unsettling assassin in Terry Pratchett's Hogfather. His approach to the latter role, in which he assumed a curious falsetto, was described by his producer as “unbelievably brave.”

“That's one way of looking at it,” Warren smiles. “The other way is that I'd just been to see Johnny Depp in Charlie and the Chocolate Factory.” Still, he could have played it much safer. “Well, the only time I feel fearless is at work.”

Growing up in Northampton, it was what he always wanted to do. “I remember looking out of the window on a drive with my dad, listening to Sergeant Pepper, thinking, I want to be an actor.” Not a musician? He giggles. “Yeah, I don't know why.”

His father, who was in the leather business, didn't pass on any creative passions, but his stylish aloofness left an impression: “My dad was a bit of loner, he always reminded me of Björn Borg.” But Northampton was “a good place to leave”, and leave he did, at 17, to become an actor in London. His break came at the age of 30, in the police series The Vice.

Since then, he has worked mainly in television, but his dedication to his roles seems better suited to cinema, with its stately production pace. He had his first real taste of Hollywood last year, moving to Los Angeles, “specifically to get a film.”

Warren remembers, rather forlornly, watching the Oscars on the telly, but he got an audition for the sci-fi thriller Wanted and was offered the part. He has no illusions about the prestige of his role (“I just punched James McAvoy”). But he had screen time with Morgan Freeman and Angelina Jolie, whom he speaks of with boyish reverence: “She has a light around her.”

One Sunday, he and McAvoy were invited go-karting with Jolie and Brad Pitt. “I'm terrified of go-karting,” he admits. “I remember walking through the door knowing that Brad was on the other side. I'm quite shy and I thought, right, just go straight up to him. He's just this beautiful, charismatic superstar [laughs]. I suddenly thought, even if I kill myself I'm going to race like f***. He was brilliant, a natural athlete, but I took him off the track a few times. I became fearless.”

He likens it to being in a team with Tony Adams. But despite his sojourn in the Premier League, he is happy where he is: “I try and do what I do well, but [Brangelina] just fit it.”

Warren, of course, is one half of a slightly less starry celebrity couple. His girlfriend, Abi Titmuss, recently confirmed their year-long relationship live on Richard & Judy. Was that annoying? “That's happened,” he shrugs. “It's partly her and it's partly Richard Madeley asking her.”

But does such openness, plus her calendars and recently published diary, jar with his more private nature? He frowns: “I do my job the best I can, but the other side of this business is celebrity and I've never understood that curiosity.” He refuses to say any more. But the attention won't go away, with the couple co-starring later this year in the same UK film, Do Elephants Pray?

Confident yet shy? Bowled over by movie stars yet left cold by celebrity? Warren lets the contradictions fly: “I used to create a persona of being incredibly together, but now I'm a lot more accepting of my flaws. People say, 'Be yourself'. There's many ways of interpreting that.”

Mutual Friends begins on BBC One next week

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