Party over for Colin?

A gritty, hard-edged affair, Miami Vice is very much a Michael Mann film, shot in the murky high-definition video he pioneered on Collateral. Brooding and atmospheric, with some spectacular shoot-outs and action set pieces, this is no straightforward crowd-pleaser. The plot is complicated and ultimately baffling, the tone aggressively masculine. In a summer when Pirates of the Caribbean 2 is the audience favourite, box office success is far from guaranteed.

Nor was it an easy shoot. The famously fastidious Mann sent Farrell and Foxx to train with real-life undercover agents in Florida.

Then the seven-month shoot was stalled by hurricanes, Katrina among them, and a shooting incident near the set in Miami. The cast was ferried to Paraguay, the Dominican Republic and Uruguay, and media scrutiny was intense, with rampant speculation that Foxx and Farrell weren't getting on.

Was it any wonder that Farrell, who always said that drinking was his way of letting off steam after a hard day's work, was seen at every club and party around Miami?

"Miami Vice was incredibly long and arduous," Farrell agrees. "You've probably heard that Michael Mann is extremely bull-headed, and he is. It was a great experience, but by the end of it I was wrecked."

At a production party in Uruguay, Farrell collapsed, and although he didn't need a hospital stay, he promptly checked himself into a treatment centre. His publicist said at the time that he was suffering from " exhaustion and a dependency on prescription medication". Anyone versed in the lingo of Hollywood can see through that one.

So has he given up drinking for good? "You know, I haven't had a drink today," he says wistfully. "I'd never say anything for good. I've said too many 'for goods' in my life that didn't last."

The new Farrell has thrown himself into his work and is focusing on the biggest love in his life, his son James, who will be three in September.

"My priority, first and foremost, is the little fellow," he says. "Talk about falling in love. It's bizarre to fall in love and know it's going to last. That's what it feels like for me. It's like nothing can come between us."

Farrell has never been known for self-analysis. But the sobriety and the break from work have clearly given him time to reflect on his dizzying rise to fame. In the past six years, he has been branded a Hollywood bad boy both for his hard-partying ways but also for his notorious womanising.

His marriage to actress Amelia Warner only lasted 10 months, and he has been linked to so many stars, Britney Spears and Angelina Jolie among them. He even made the fatal mistake of videoing a sex session with former Playboy Playmate Nicole Narain, which - how could it not? - surfaced on the internet.

When model Kim Bordenave claimed she was pregnant with his child after the briefest of relationships, Farrell was expected to dispute the claim but quickly accepted paternity. Six weeks after James was born, Farrell met him for the first time on a landing strip in the Moroccan desert where he was filming Alexander.

"I want to be alive for a long time and watch him grow up and be his friend and father," he says. "I never had that much of a reason to live for a long time. There were reasons there - my two sisters, my brother, my mother, my friends, the work - but I decided they weren't reason enough."

It's a mystery why Farrell has never achieved the major hits which Hollywood was expecting after the dark, charismatic Irishman burst onto the scene. Born in Dublin, the son of a soccer-player father, he always fancied a life as a performer and even auditioned for the band Boyzone when he was a teenager before a year at acting school, Dublin's National Performing Arts School and the Gaiety School of Acting. His big break came in 1998, as Danny Byrne in hit TV series Ballykissangel, which led to his London stage acting debut in In a Little World of Our Own at the Donmar Warehouse.

He soon had LA calling, and it was a short hop to Tigerland, Joel Schumacher's military drama in which he blazed onto the Hollywood radar.

But a supporting role in blockbuster Minorty Report didn't compensate for leads in a string of mediocre movies - The Recruit, Hart's War, Phone Booth, Daredevil and SWAT. If Farrell's bright new star was beginning to lose its lustre, it hit a career low when Oliver Stone's $200 million epic Alexander, in which he played Alexander the Great, received some of the worst reviews of his or any career in 2004.

"I personally took a huge hit on Alexander," he reflects. "It affected me greatly. The critics tore the film to pieces in a very lascivious way and it was hard to see something you cared about incredibly being ripped to shit before your very eyes. There's nothing you can do, because people are within their rights to have opinions."

The box-office failure of his next film, The New World, for legendary director Terrence Malick, did nothing to boost Farrell's profile, although his absence from the publicity rounds and premiere didn't help either. He was in rehab at the time.

But film-makers and studios continue to bank on Farrell, whom they see as a fine, classically trained actor and a magnet for publicity. He has also made sure he starred in some smaller, more artful and edgy films along the way to cement his serious reputation, such as A Home at the End of the World, in which he shared a gay kiss on screen, period drama Ask the Dust, and Irish crime ensemble Intermission.

Next up is Pride and Glory, in which he and Edward Norton play members of a family of three generations of New York cops, and the Woody Allen film, a drama in which he and Ewan McGregor play brothers from the East End who turn to crime and end up as enemies. He can't say much about it, he says, or "Woody would go mental". Early next year, he will team up with Oscar-winning London-Irish playwright Martin McDonagh on his directorial debut, In Bruges.

And still, though he doesn't seem agitated, Farrell admits that he isn't especially satisfied with his lot. "I could be looking for something I'm never going to find," he says. "There's certainly an argument that I use work as a distraction, as something that can keep me involved. At least on a film set I know why I'm there. I know what my purpose in life is. Sometimes I start a film with high hopes, and then at the end I think, 'God, I fucked up', and go and do the next one, thinking that will be the one.

"Priorities shift," he concludes. "On achieving the thing you want, sometimes you realise its lack of importance. I think that's why sometimes you count your blessings, realise how fortunate you are. After Miami Vice, I got to kind of take the deep metaphorical breath. And it's good. I needed it."

Miami Vice opens on 4 August.