There’s an air of the rake about Jonathan Rhys Meyers. It’s not just his work, from his Bowie-inspired breakthrough in Velvet Goldmine to his sensational turn as Henry VIII in The Tudors. There’s more to it than that. It’s something to do with the physicality of this Irishman, the way he holds himself in company. Late from introducing a screening of his new movie August Rush at the Rome Film Festival, when he arrives for our meeting in a dinner jacket and open-necked dress shirt, he looks like the chief casualty of a very debauched party.

Not that he indulges in such things nowadays: after a brief pit-stop in rehab earlier this year for alcohol abuse, the untouched packet of Marlboro Lights in his pocket points to Rhys Meyers’s only vice. As he sits down, directing those smouldering blue eyes on me, he is fresh-faced and businesslike. Indeed, he is a master of self-promotion, mentioning twice that he won the Golden Globe for the CBS TV movie Elvis and oozes confidence. “I completely believe that I will produce my best work in my thirties,” he says, in his soft Irish lilt.

He turned 30 in July and likes the feeling. “I wouldn’t want to do the twenties again. It’s a strange thing but you do feel more mature. You always view yourself as a kid. You don’t feel any older or younger. But then I noticed that in the last two years how people view you. You’re now one of the grown folks. When little kids come up to me, I’m a fully-grown adult, and that’s always weird to me. They expect you to be the responsible one. And I’m like, ‘But I’m a kid just like you’, but then I look in the mirror and I’m not.”

This brings us neatly on to August Rush, a modern-day fable about a musical prodigy (played by Freddie Highmore) who sets out to find the parents he was separated from at birth. Had he been acting as a child, Rhys Meyers would surely have been precocious enough to play the title role – not least because his own folk musician father left the family when he was aged 2. In fact, he plays August’s father, Louis, a singer in an Irish rock band, who meets August’s mother Lyla (Keri Russell), a cellist, for a single night of passion.

The film is really about the ability of music to connect us all – as shown by August. “He hears music on a completely different level,” says Rhys Meyers. “Music is his air. It’s his lifeblood. It’s his food and his water. He’s kind of like a little Mozart.”

Including enough sugar to rot your teeth, this is not a film for the cynical. “To get the most out of it, you have to allow yourself to see the world through August’s eyes, which are much more magical than an adult’s.” The father’s story, as he hankers after Lyla, is just as much fairytale. “It’s that possibility,” the actor says. “Can you fall in love at first sight and does that love ever leave you?”

I ask Rhys Meyers if he believes in such romantic encounters. “I completely believe in love at first sight,” he sighs. Has it happened to you? “Mmm. Think so. Yeah,” he says, but adds no more. Is he single? “I’ve been seeing my girlfriend again, Reena [Hammer],” he says, hinting how on-off his relationship is with the 20-year-old student and heiress to the Ruby & Millie cosmetics line. It certainly seems stormy; back in 2005,Rhys Meyers and Hammer were arrested after a stormy altercation at their North London home.

Yet it can’t be easy for Hammer, particularly now The Tudors has turned her man into a sex symbol. Rhys Meyers, who played a slimline Henry makes no apologies for the bodice-ripping. “We’re not making a documentary for the History Channel. When people say, ‘The sex is a little bit too much,’ well listen guys, they didn’t have a hell of a lot else to do in the evenings! Sex was a very important part of their lives. They didn’t have TVs, or iPods or newspapers. Any entertainment they had, they had to make for themselves.”

His portrayal has won approval from the historian Lady Antonia Fraser. “The only thing that she wasdisappointed about is that I should have had red hair.” The series has been a hit in America and more awards for Rhys Meyers seem certain.

However, the actor’s ascent was hardly preordained. He grew up in a Cork council house and, with no father to guide him, became a childhood terror. “I just didn’t go to school,” he says. “I felt I could educate myself better than they could educate me. They were teaching me stuff I had f***-all interest in.” Expelled at 16, he was caught driving without documents and reckons he was heading for juvenile centre when a chance encounter with a casting director changed his life. “Luck came along and I pushed it as far as it would go,” he says.

Put up for a David Puttnam film, he didn’t get the part and “felt utterlyrejected” but had found a new purpose. He travelled three times weekly for a year to Dublin for auditions. “It felt like I was fighting Mike Tyson, because I kept getting rejected. I was punched and punched but I refused to go down.”

His first success was the lead in the low-budget The Disappearance of Finbar, swiftly followed by a bit-part in Neil Jordan’s Michael Collins before Velvet Goldmine. After this, parts were diverse – a Civil War cowpoke in Ang Lee’s Ride with the Devil,Steer-pike in the BBC adaptation of the Gormenghast novels and a football coach in Bend it Like Beckham – but, as he proudly notes: “I stayed employed all the way through my twenties. And that’s difficult.” He went on to play one of Tom Cruise’s fellow agents in Mission: Impossible III,but it was probably taking the lead in Woody Allen’s Match Point, as an ambitious young man who turns to murder, which changed perceptions of him. “Now the stuff that I’m getting is very much leading-man material,” he says.

He has just filmed the role of George Hogg, a real-life journalist in occupied Shanghai during the Second World War in The Children of Huang Shi and there’s talk that he might play Napoleon – a long-standing ambition – in Danny Glover’s Toussaint. Hollywood is in his sights now: if he’s not learning lines or courting casting directors, he’s working up a sweat in the gym to adopt that Alist look. “If you want to be at the top of your game, you can’t be out partying with your friends or having six pints a night.”

This rake’s progress is clearly set to continue.

August Rush is released nationwide on November 23

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