FIRTH PERSON SINGULAR

If Colin Firth has a problem in life, it must be persuading people that he was not the star of the film Equus. Colin Firth is no relation to Peter Firth, who was. And, what is more, Peter Firth was yesterday's hero. Colin Firth is today's - and tomorrow's.

At 28, he shows every sign of making an international name for himself. As if to prove it, he flies in hours before our interview from the South of France, where he has been filming with Peter O'Toole ("Wings of Fame"). A couple of days in London and he's flying off again to southern California where his girlfriend Meg Tilly is filming with Jack Nicholson. He's only over here at all to publicise Apartment Zero, now showing in London. For someone who lives in Hackney, Colin Firth spends a lot of time in more glamorous climes.

Perhaps it's no wonder he feels a shade fatigued. "Do you mind if I lie down?" he asks suddenly, slumping on to the couch in the distributor's office, brown suede boots placed neatly by its side. It obviously makes him feel a lot more comfortable. I feel like his analyst. Not that you get the impression he has much need of one.

Colin Firth's career got off to a flying start. Fresh out of drama school, he was invited to join the cast of Another Country, then already a West End theatre legend. He took the leading role of Guy Bennett, the part made famous by Rupert Everett. When Another Country was filmed a little later, he played Judd, the second lead and the part originally played by Kenneth Branagh.

As a first act, this could have been hard to follow. In fact, the young actor found himself playing the romantic lead opposite Greta Scacchi in Camille, and the lead in a TV series called Lost Empires. A "rubbish phase" he calls it.

But no one could call some of his recent parts rubbish - including, as they do, the hero of Tumbledown, the real-life story of the Scots Guards lieutenant hideously injured in the Falklands War. It attracted award nominations and flack in about equal measure. As a piece of acting it was "as easy as falling off a log."

This is not an insensitive remark. "I don't want to belittle the character," Firth says. "And no, I didn't play that part without some cost to myself. But the only thing that was difficult was to do it courageously, to have the guts and the honesty not to show off. Anyone can cry, and laugh, and go charging into battle. As a piece of acting, it was standard drama school stuff. What's hard is to play someone normal, decent, sane."

It is clear why Martin Donovan, Apartment Zero's director, was keen on Firth. Donovan saw Another Country both on stage and screen. He'd liked the actor who played Bennett in the one, and the actor who played Judd  in the other, but didn't realise they were the same. When he found out, his way was clear.

Apartment Zero is a psychological drama ("thriller is misleading, horror film is absurd") set in Argentina. It is about the relationship between two young men, set against a backdrop of political murders. Hart Bochner plays the mysterious American who comes to lodge with a repressed and paranoid Anglophile (Firth), an Argentinian who actually carries a rolled-up umbrella and lives behind Harrods in Buenos Aires. Several times you think you've figured out what there is between them. Each time, you realise you were wrong.

"People sometimes ask me why I tend to catch all the neurotic characters. But what else is there that you'd want to do? Romantic young lovers bore me to death." In the title role of his other new movie, Valmont, Firth may be playing one of the world's great seducers. But romantic? Never.

Valmont, opening in America later this autumn, is director Milos (One Flew Over The Cuckoo's Nest) Forman's version of Les Liaisons Dangereuses. It is a big affair, with a budget of $35 million and a schedule that went on for ever. Firth took the leading role seriously.

"I don't think I'm a steamy, smouldering kind of guy. I haven't got the eyebrows for it. I had to decide that Valmont's power over women wasn't because he was just so sexy, otherwise I'd have been racked with insecurity.

"Anyone can seduce members of the opposite sex. The thing about Valmont is that he's a manipulator."

Playing a man who deliberately ruins two women for the sake of a bet with a third (Meg Tilly plays the most innocent of his victims - the couple met while filming), Firth naturally assumed that he'd been cast against type. "They wanted someone who didn't look dangerous," he says. Imagine his feelings when someone said to him: "Milos is so clever. He always sees straight to the heart of the people he casts."

"To my horror, I realised it was partly true. I can use people. I am a manipulator. I am very good at getting what I want in life." So what does Colin Firth want now?

The answer, at the moment, is that he wants a break. Not just because he's exhausted (he's going to America, he says, to "convalesce"), but because he feels it's time to stop and think a little. To think about what comes next - and that, he hazards, may not be acting. "The thought of reaching 40 and not having grown out of this is horrible." No, he doesn't know-what else he'd do. "I just want to be more normal..."

It's almost five years since I first interviewed Colin Firth. He was still the new boy then. I wrote the piece, handed it over, and came back from holiday to find it printed with the headline "Simon Firth - a face to watch out for." Firth's reaction was: "How lucky they didn't put 'A name to remember.'" 

• "Apartment Zero" is now showing in London's West End; and opens nationwide from November.