Colin Firth is fielding NOW’s eager questions on the subject of him baring all for steamy sex scenes in his new movie Where The Truth Lies.  He’d probably rather talk about the film’s gritty plot—he plays Vince, whose showbiz partnership is destroyed by an unexplained death.  Matters only come to a head years later when a journalist uncovers the incident and becomes sexually and emotionally involved.  But, for now, back to that on-screen nudity... ‘It’s very hard to reach the end of your life as an actor without getting your kit off,’ says Colin, who turns 45 on 10 September, ‘but it’s not my favourite thing.  Some people hate it, others would positively enjoy it, but, at best, I find it a little weird. ‘You come to work, have breakfast, shake hands, take your clothes off, leap on top of a gorgeous-looking actress and pretend to have sex with her.  I was relieved not to be there for more of it, to be honest.  By the time I’d started, the film set had been closed to visitors and my co-star Kevin Bacon had been humping away for about a week.  So they were like veterans and the film crew were yawning.  When I walked on, all ready to go, with a flesh-coloured pouch covering my privates, no one took any interest.’ And what’s the reaction of his wife, Italian documentary maker Livia Giuggioli, with whom he has two sons Luca, four, and Mateo, two?  ‘She’s alright—I think,’ he says.  ‘Anyone who’s married to an actor has to get used to it happening a lot.  She knows what’s real—or not—so she’s cool about it.

‘Whatever people say, what’s happening on screen has nothing to do with your personal feelings towards the actress.  I’ve been on film sets where couples have to make love and all the critics later rave about their “chemistry”.  But they actually disliked each other—and the only thing we were seeing was good acting.’

But Colin is uncertain as to what audiences will think of Where The Truth Lies when they see it later this year.  ‘I’m not even sure who this film is pitched at,’ he says.  ‘I never think along those lines.  I’ve been working away at edgy stuff for years and it doesn’t seem to get noticed.  But things like Darcy stick to your skin.’

However, Colin isn’t running down his famous role.  ‘It came like a time bomb, just waiting to go off,’ he says.  ‘But I nearly turned it down because I couldn’t have been more wrong for the role.  I’m totally unlike Darcy.  I talk a lot, I don’t own a horse and I don’t have a wonderful home in Derbyshire.  I’m a secondary modern schoolkid who doesn’t belong to nobility.

‘I was saying: “He’s this taciturn, sexy guy—and that’s just not me.”  The only thing we shared was nationality.  But the time had come for another costume drama—and Darcy was noticed.’

So, was Colin glad that he took the plunge?  ‘I’m proud of it and grateful,’ he says.  ‘It’s something that people remember fondly—and they remember me for that role.  I wouldn’t have been in two Bridget Jones films without Darcy.  I did find the publicity a bit of a shock at the time, but I take the sensible view: “Where would I be without it?”

Even he was surprised at the runaway success of Bridget Jones’s Diary.  ‘It wasn’t conceived as a blockbuster,’ he says.  ‘Everyone was nervous.  There’d been a lot of criticism about having an American actress like Renée Zellweger playing Bridget and me reprising Mr Darcy.  Everything was insane.

‘But the second Bridget film, last year, was completely different.  We all knew that Renée worked well and that audiences accepted me playing Mark Darcy like Mr Darcy.  There was also a lot more money behind it.  I find that in film-making nothing comes with assurances.  There’s always a risk—and things can go wrong at any time.’

But Colin has a down-to-earth view of fame.  ‘Once you’re a celebrity, it seems that you don’t play by the same rules as the rest of society,’ he says.  ‘People will be nice to you all day long for no other reason than that they’ve seen you in movies.  So you need to find something other than your fame to give you strength and some meaning to your life.  Otherwise you can end up in rehab—or worse.  A lot of people fall apart because they get too much of it.  Those are the people who, when I look back, had nothing more than celebrity going to keep them going.’

What’s kept Colin so sane?  ‘My family, my wife and children and a handful of close friends,’ he replies.  ‘If I get less money and less fame, it doesn’t matter to me.’

Colin also has a teenage son William from a relationship with American actress Meg Tilly, with whom he co-starred in the 1989 film Valmont.  ‘We have great relationship and I see him a lot,’ he says.

‘I’ve never been an enormous star.  The tragedy can be that when you’ve had a career that’s soared, there’s nowhere to go but to fall.  The stakes are so high.

‘I’ve also done plenty of things that haven’t worked.  That old phrase about learning from your mistakes is true.  My best work has come after something has failed.’

Colin will next be seen on screen co-starring with Emma Thompson in Nanny McPhee, set to be released on 21 October. [Note: UK only]  The children’s story about magic couldn’t be more different from Where The Truth Lies.

‘It’s very hard to talk about Emma Thompson without making people vomit,’ he says.  ‘She’s an intellectual with enormous talent as a writer and actress.  She also takes care of people on the film set, is a wonderful mother and is heavily involved in charity work.  And she doesn’t trumpet any of this.

‘So I’d have to say that working with her is the easiest thing in the world.  She’ll always deliver great acting and won’t show you up.’

And has she seen him naked in Where The Truth Lies?  I hope not—for her sake,’ he says.