James Nesbit: It's time to act serious

James Nesbitt made his name as the irrepressible Adam in Cold Feet, but as Tommy in Murphy's Law, back on BBC1, he's in much darker territory. That's what drew him to the role, he tells James Rampton

Tommy Murphy is livid. He has caught his estranged wife in bed with a younger man and pulled a gun on him. His wife intervenes, desperate to break up the cockfight. "Oh Tommy,'' she pleads, "What we had together was great – don't spoil it.''

"What we had together is buried in Roselawn Cemetery,'' he shouts back at her heartlessly. She runs to the bathroom in floods of tears, distraught that her husband has raked up the memory of their young daughter, who was killed as a result of his job as an undercover cop.

Tommy, the title character in Murphy's Law, which returned to BBC1 for a full series last night after a successful pilot two years ago, is a deeply troubled man. He's played by James Nesbitt, for whom the part was specially written by Colin Bateman (Divorcing Jack). Tommy is a far cry from the role for which Nesbitt is best known – Adam in Cold Feet, ITV1's warm thirtysomething saga. He was a character for whom the term "cheeky chappie'' could have been invented. Where Adam was mischievous, Tommy's just miserable.

It is lunchtime on the Murphy's Law set. Dressed in T-shirt and jeans, the 37-year-old Northern Irish actor is unwinding in his caravan on one of those depressing expanses of east London wasteland so favoured by film units. Eschewing the runner's kind offer of apple crumble – "My body is my temple,'' he says with a characteristic wry grin – Nesbitt settles back on the sofa and explains what makes Murphy tick.

"He's cocooned in his own world. Now that his daughter has died, he doesn't care about anything. Her death is key to his character. He'll be damaged until the end of time – you would be, if your daughter died and you felt responsible for it.

"The only thing that's keeping him alive is his job as an undercover cop. He's desperate to work because by being undercover, you're hiding from yourself and you don't have to think about what's happened. He hasn't exactly got a death wish, but he certainly has no fear – nothing can be worse than what's happened to him already. And that's what makes him so good at his job.''

It's also what makes Tommy so different from the adorable Adam, who managed to retain his essential good humour after the death of Rachel, his wife and the mother of their baby, in a bolt-from-the-blue car crash during the penultimate episode of Cold Feet.

Murphy reacts to grief in a much more bitter and traumatised fashion. But it is this very difference that drew the actor to the role in the first place. He trusts that viewers will be surprised by his performance. "I hope they think, 'Oh God, he is in fact an actor and not just one character.' My real worry has always been that it will become a problem to leave behind the public perception of Cold Feet.

"You can become lazy playing just one character, but I hope that roles such as this will help me get away from Adam. I don't want to be doing variations on Cold Feet for ever. It's important always to be moving forward and to be challenged, otherwise I may as well work in a bank.''

So Murphy's Law appealed because it is very much "a departure'', Nesbitt says. "Given the type of actor I am, the fact that this is dark makes it very interesting. What has happened to Murphy and his daughter gives you extraordinary scope as an actor. There's a hell of a lot to him. Sometimes I may even go too dark in this role, but that stems from me thinking, 'Am I being too similar to Adam?'"

In person, Nesbitt is every bit as winning as Adam, and he demonstrates a likeable readiness to send up his Mr Nice Guy reputation. "'Charming' is a bit of a tired euphemism that critics use when they can't think of anything else,'' he laughs. "It covers a huge area. My mother certainly doesn't think I'm charming."

But his image was tarnished in December when the tabloids alleged that Nesbitt – married, with two young children – had had an affair. However, he appears to have salvaged his marriage after a public mea culpa. "It has been a desperate time. I acted like an eejit. I let a lot of people down and for that I apologise.''

He is much happier talking about the new, more serious direction his acting is taking. Starring in last year's Bloody Sunday, ITV1's acclaimed docu-drama, gave the actor the taste for roles with visible darkness. The actor won a Bafta best actor nomination for his memorable performance as Ivan Cooper, the civil rights leader, in Paul Greengrass's film about the 1972 killings in Londonderry.

Even though Nesbitt, a Protestant from Broughshane in County Antrim, was on the receiving end of some stern criticism from the Unionist community for participating in the project, he obviously relished the experience. "Nothing has had the impact that Bloody Sunday has had on me,'' he says. "The film might turn out to be a watershed for me. For years, acting was something I enjoyed but couldn't take seriously. But making Bloody Sunday made me feel less guilty about my job. It made me realise that there is worth in acting."

He found the production so rewarding that he is hoping to collaborate with Greengrass again on a film about the Omagh bombing in 1998. "Eamonn McCann wrote a marvellous piece after Omagh saying that Bloody Sunday made war inevitable and Omagh made peace unavoidable,'' Nesbitt reflects. "Omagh cut a swath through all denominations – more Catholics died there than anyone else. It went right to the heart of what we thought had come to an end. It's a story that needs to be told.''

But is he concerned, that, like Bloody Sunday, a film about Omagh would whip up controversy? "What can you do?'' Nesbitt asks. "Should it stop you doing your job? Should an actor refuse to play Hitler? I wouldn't want to get drawn into a media furore where everything I say gets taken apart and regurgitated in the wrong way, but that wouldn't stop me making the Omagh film. If a project is worthwhile, then I'll do it.''

Nesbitt's career has never looked healthier. He has been so much in demand that he even had to turn down a good part in Richard Curtis's latest comedy, Love Actually. No longer cast merely as an irrepressibly chirpy lad, the actor seems to be developing a welcome versatility.

But for all his current popularity, he remains appealingly self-deprecating. Whether he is playing light or shade, Nesbitt has never taken success for granted. "I never forget that I am extremely fortunate. I get paid very well to turn up and say a few lines. It's very hard to complain about that because it's an extraordinarily privileged position,'' Nesbitt says, before flashing me the last of his trademark grins. "It's not as if I'm going down a mine every morning, is it?"

'Murphy's Law' is on Mondays at 8.30pm on BBC1