Is that Mr Darcy taking part in an orgy?     The cocktail of drugs, sleaze and sex in their new film, Where the Truth Lies, might shock some of Colin Firth and Kevin Bacon's fans. They talk to Sheila Johnston

At early screenings of Colin Firth's new film, Where the Truth Lies, it was hard to know what confounded his fans most.

Was it his presence as the ham in the sandwich, as it were, of a three-way, bisexual orgy? His generous pill-popping? The scene in which he batters a bystander to within an inch of his life? Or, most alarming of all, perhaps, the spectacle of Britain's eminent heartthrob in naff 1970s vintage sideburns, moustache, hipster trousers and gold chain?

The film begins in the late 1950s when Vince, Firth's character, forms half of a phenomenally popular lounge act: the cool, debonair straight man to Kevin Bacon's brash, manic comic.

Offstage, both men's voracious and mostly illegal appetites draw them into a scandal that ends their partnership. Then 15 years later, after the two have long since gone their separate ways and entered discreet semi-retirement, a nosy female journalist (Alison Lohman) starts to probe their story.

Despite raised eyebrows at the film's world première in Cannes, Firth's performance should not have come as too much of a surprise; after all, as he helpfully pointed out, to play a drug-addled swinger hardly requires a great leap of imagination for most actors, and certainly involved rather less research than Mr Darcy, the lord of the manor from Derbyshire.

Ten years after that iconic role in the BBC's Pride and Prejudice, Firth has placidly resigned himself to embracing Darcy's memory. In the two Bridget Jones films, he played an ironic modern version of the character, and now Where the Truth Lies draws knowingly on that suave, cultivated persona.

The original novel, by Rupert Holmes, was widely supposed to be a roman à clef about the spontaneous combustion of the relationship between Jerry Lewis and Dean Martin.

In it, Vince was an Italian-American singer. "I've got some crooning issues—or rather, other people around me have them," Firth says. "But I would have loved to have a go at playing Vince as an American and I felt it was within my grasp." However, in the film the character has become immaculately British. "I realised," he says, "that it was valuable to bring my baggage and use a bit of the Darcy thing."

The film's director, Atom Egoyan, cast Firth partly to avoid "irrelevant" echoes of the Martin-Lewis story (and, possibly, any attendant litigation).

He conceived the character as a composite of David Niven, Rex Harrison and Noël Coward, and says he was attracted to the "veneer of civilisation" that Firth could bring to the role.
    
But Egoyan adds: "I've also seen him be really brutal in earlier work, like Tumbledown [the 1987 BBC drama], where he was absolutely terrifying as a Falklands soldier. He used to play much darker characters, and I thought it would be great to summon that up, even if some people will be shocked that Vince is so reprehensible."

Firth and Bacon had never met before making Where the Truth Lies. None the less the director, somewhat dauntingly, expected them to devise their own comedy routine from scratch, apparently even hiring a "professional laugher" to encourage them in their efforts.

Happily, the chemistry between the two actors appears to have gelled; in interview together they perform as a double act, with a barbed but friendly line in mutual banter.

"He gave me silk boxers from Harrods as a wrap present, so that gives you an indication of how we got on," Bacon reveals.

Firth counters, "I just wanted him to wear something. We've been through a lot on this movie and there are things I never want to see again. [To Bacon] You gave me a nice silver thing, which I thought was a bit camp, actually, with a very suggestive engraving on it."

The film's cocktail of drugs, sleaze and sex—in particular that three-way encounter between Firth, Bacon and an impressionable chambermaid played by Rachel Blanchard—caused a minor scandal and attracted the unwelcome attentions of the American censor.

After a series of arguments, Where the Truth Lies was released in the US unrated, due, reportedly, to an excess of "thrusting"; it will have an 18 certificate when it opens here on Friday.

Aside from its more lubricious elements, one of its presiding themes is the shifting sands of showbusiness and, in particular, the seismic shift between the star-struck 1950s and the ruthless 1970s when celebrities' secret lives became fair game for the media.

It's something that both Firth and Bacon—though both men's lives are mercifully scandal-free—are well-placed to comment on.

"My parents get weird phone calls and people showing up at their house," Firth says. "They're innocent about it—they want to be nice to absolutely everybody because that's the kind of people they are, and they answer questions politely. Then they'll get me on the phone saying, 'How could you tell them about the Batman outfit I had when I was 19?' The press are pretty determined and they'll do anything. It doesn't matter to them what the wreckage is in someone's life after the one-day story."

"In the 1950s there was much more of a wall protecting the stars," adds Bacon. "The media co-operated more, there was no internet and you couldn't tap into somebody's cellphone. You've gotta keep it in your pants more these days.

"I would say 95 per cent of being famous is pretty good and the other part, the idea that you are never anonymous, is a strange kind of jail sentence. Personally I don't like to complain about it too much, because I worked my whole life to become famous—that's what you do if you're an actor—but for my children it's a real invasion."

Bacon, whose own first major box-office hit was Footloose in 1984, has been hovering on the edge of major stardom ever since (most people now probably identify him most with the game he inspired, Six Degrees of Kevin Bacon, which recently spawned both a book and a photography exhibition).

Firth, meanwhile, is girding his loins to play a Roman soldier in a historical drama called The Last Legion. "I wear a little mini skirt and a thong," he reveals.

Bacon sees his chance for one last parting shot, and seizes it immediately. "Yup," he chimes in. "You'll be swinging your lance around all over again."