As diversionary strategies go, it's as neat as they come. Unfortunately, Mr Gullible sitting opposite him today doesn't immediately recognise it as such. In retrospect it's blindingly obvious. Flanagan, the Easterhouse boy who's now more familiar with Hollywood soundstages, is not one for self-revelation. He's charming, yes; entertaining, sure; but he's also rather cagey.

There may be good reasons for this. When he first started talking to the press after he got his first big movie break in Braveheart, the subsequent interviews were garlanded with headlines like ''A scar is born'' and ''Braveheart made me a superscar'', much to Flanagan's annoyance. ''F-ing idiots'' is his considered opinion of my fellow journalists. Then there's the fact that he comes from a big family who will put him in his place if he says the wrong thing. As he says at one point: ''You cannae bullshit a Glaswegian.'' Or maybe it's that he feels his past is a foreign country - a wilder, darker place that he'd rather not revisit.

Actually I seem to have got him on a good day. At one point, talking reasonably openly about his family background, he stops short and looks at me. ''I forget I'm talking to a journalist here. I'd better shut up.'' Months later when I speak to him a second time, he simply admits, ''I'm not good at these things. I can sit and have a conversation with anybody, but as soon as I think it's going to go into print I just clam up and do not have a f-ing clue what to say. I think it's my interesting past. I'm just a withdrawn person, I suppose. I've recently found out I'm an extrovert when I'm drunk and an introvert when I'm sober.''

And so he's happier talking about the time he brought Joaquin Phoenix to Glasgow for a long weekend, or making movies with Ice Cube. Or indeed Peter O'Toole.

The anecdote goes like this. Flanagan and O'Toole are sat on Malibu Beach - Malibu being the place Flanagan is calling home the first time we speak. ''I was telling him my life story,'' Flanagan explains, which prompted the Irishman to stir up a memory of Scotland, told in Flanagan's best O'Toole impersonation (which, frankly, could use some work). ''I was in Glasgow doing my national service in the fifties,'' O'Toole told him. ''I was in a bar called the Sawry Head? Do you know it?''

''The Sarry Heid, aye.''

''I'd just got off the boat and all these Teddy boys were in there. They all looked at me and I thought I should leave. So I walked out the pub, but I could hear them behind me like a pack of wolves in crepe shoes. Do you know they chased me all the way to Paisley?''

''We were at the Malibu shoreline,'' Flanagan continues, ''and he said: 'how far along the coast is that?' I said it's basically the other side of the world. 'That's Paisley away over there.' He went: 'Really? Christ, I must have been fit.'''

Perhaps it's appropriate that O'Toole's name should surface this afternoon. We are sitting in a bar after all. It's high summer in Glasgow and Flanagan is back in the city of his birth after shooting his latest film, Trauma, an itchy psychological thriller starring Colin Firth in which Flanagan plays a Glaswegian painter and decorator called Tommy. ''Ooh, there's a stretch,'' he mocks. Tonight he's off to London to pack up his flat before heading back to LA and the next job. But for now we're sitting in a designer bar in Bath Street.

To begin with it's just me. Flanagan rolls up 20 minutes late in sunglasses. Thankfully this is not a nascent Hollywood hauteur, but an antidote to the white noise of a killer hangover.

''What day is this? Tuesday? Christ, I've lost track of a day.'' Sounds like a good party. ''Very good. You can see it was a good party,'' he says, a nod to his squinting, headachey demeanour. He's been celebrating his brother Danny's 40th birthday, a celebration that began on Sunday. ''The last time I drank was a year ago, so I feel really bad actually. But it was fun.''

Besides Trauma he will appear later this year alongside fellow Scot Ewen Bremner in a fanboy's wet dream of a movie, Alien vs Predator, in which he plays a soldier of fortune. He won't tell me if it's the alien or the predator that gets him. He won't even tell me if he dies at all, though since the movie tagline is ''Whoever wins, we lose''. I'm guessing he might not see the end credits. He's also up for a lead role in a new television series set in Boston which sounds like an Irish Sopranos. Oh yeah and then there's his own project. Schemes, Dreams and Heartaches, a semi-autobiographical project that American producers are keen on doing with him. He's writing it himself. Actually, he's a little reticent to say quite how much of his own story will make it onto the screen. But then he seems even more reticent about the idea of it getting onto the page.

Spend any time talking to Tommy Flanagan and you quickly forget about the scar that loops and curls around the bottom half of his face. His defacement doesn't define him. He says most of the time he doesn't notice it himself. ''Sometimes you wake up and see it,'' he admits, ''but most of the time I don't notice it any more. You cannae think about it. The only time I ever think about it is when I'm back here in Glasgow. Chib city.''

The great thing, he says, is that Hollywood doesn't take much notice of it either. Sure, he's played his fair share of hard men, like in Charlie's Angels: Full Throttle, but that's hardly a chore. ''You get to have your ass kicked by Cameron Diaz, Lucy Liu and Drew Barrymore. What's bad about that?'' Who gave you the best ass-kicking? ''That'd be Lucy.''

But no, he's never really been typecast. ''You'd think I would be because of this,'' he says, indicating his cheek, ''but in the US they don't seem to see the scar.''

The scar itself is not something he particularly wants to talk about. You can thank those early headlines for that. The story I've read is that it happened in his DJing days. Coming out of a pub one night he was confronted by some guys who wanted his coat and his records. He didn't want to give them up, so they left with him with a present instead. All Flanagan will say is that the experience changed his life.

''It's a long road, put it that way. It took me a while. I just dealt with it. I could have died.'' He pauses a moment, before continuing. ''It was a bizarre thing. It was the worst thing and the best thing that ever happened to me, because I started acting after it and I had never thought about that before, and I stepped into something that I loved doing.''

Robert Carlyle and Caroline Paterson, then running Raindog Theatre, gave him a way in. He had known them before. ''I used to go out with Caroline's niece. They saw what was happening and they said 'come and try this' and I went 'OK'.

''It was bizarre. They asked me and four weeks later I was on the stage, petrified. It was the most terrifying thing in my life. That was scarier than getting stabbed or knifed.''

But he felt the fear and did it anyway. Within a couple of years he'd got himself a part in Braveheart and in 1996 he decamped to LA. Not for his career particularly: ''Naw, it was a relationship thing.'' Rachel, his girlfriend at the time, later his wife, was from San Diego and he followed her home. Still, going to the west coast didn't hurt his acting ambitions. By the start of the new century he'd racked up roles in such Hollywood fare as Face/Off, The Game, The Saint (not his favourite movie experience: leaning into my tape recorder he says slowly and precisely: ''Val Kilmer's a prick''), All About the Benjamins (one day on South Beach, Ice Cube turned to him and asked: ''So, Tommy Flanagan. Is that a made-up name?) and Gladiator. Oh and he also managed to pop home at one point to make some little movie called Ratcatcher. Well, I say little. He doesn't agree. ''Ratcatcher's huge. Drew

Barrymore called me and asked me to be in Charlie's Angels because she saw Ratcatcher.'' Unfortunately, his marriage wasn't so successful: a divorce is imminent.

The way he describes it, work is all he does. You would think living in Malibu there would be plenty of distractions, but he says not. ''Done a bit of surfing. Well I tried surfing, failed miserably. I got dragged along the bottom of the Pacific. Came up covered in bruises and black eyes and whatever. I'm not doing that again.'' Sometimes, he says, he'll pop down to an LA bar a mate of his owns called The Cat and Fiddle. It's on Sunset and sounds like an expats' watering hole. He's mates with ''little Tim'' Burgess of The Charlatans. But otherwise, he says, he lives a ''very quiet, boring life''. He looks over his sunglasses at me. ''I'm sure you're buying that one. But basically I do. I walk my dog a lot that's about it.'' (Now that he's back in London little seems to have changed. When he's got any free time he hangs out with friends, though his dog is no longer with us. ''Poor little bastard.'')

The birthday celebrations seem to have been something of a one-off. ''Yeah, I've cut all that crap. Nice healthy living boy these days. Very boring but I feel a lot healthier.'' Instead he works; in recent years he's lived out of a suitcase. ''I'm the kind of gypsy of the family.''

It's a big family. Two brothers and two sisters. Tommy is the middle of the five, with a brother and sister on either side. Then there's the five nieces and a nephew and his mother, Betty, who sounds like one of those working-class superwomen. ''She's very cool,'' Flanagan says. ''She's great actually.'' As a youngster, he says, she was very intelligent, even won a scholarship. ''But she was the eldest of the family, so she had to leave school to help support the family. Then she went back to night school, to college, university and did a degree about 40 years later, after she'd had five kids.''

Betty worked in a bar to support her children. It's safe to say she didn't always get help from Mr Flanagan. Danny Flanagan left when Tommy was a boy. ''I think officially I was 11 years old or something, but he was back and forth a lot,'' he says. '' I think it affected my (younger) brother and sister more than it affected me. I think I kind of got used to the idea over the years, you know, so when he finally left it was like I was expecting it. But my younger brother and sister were kind of confused by the whole thing.'' Danny died last year. ''I never got the chance to see him before he went.'' He starts talking about a lack of closure before remembering he's in Glasgow.

Easterhouse, he says, was wild back in the seventies. ''There was a lot of mad gang stuff but I wasn't involved in that. It was a bad place. We used to sit and watch all these pitched battles on the playing fields, sit next to school and watch them going back and forth. It was like watching Braveheart again.'' The chronology is a bit askew there, but you know what he means.

He was, he says, OK at school, but left early for a life of YOP schemes, then painting and decorating for some ''dodgy outfit''. There wasn't any real plan to it all. There still isn't, he says, he's ''still coasting through life''.

In the late 1980s he turned his hand to DJing. ''I went to Greece and I was DJing over there and I came back and the whole acid rave thing had all kicked off and I started playing all these clubs, couple of raves and that. I had a good time, too good a time. Yeah I was very into business when I was a kid, then in my 20s I started DJing and partying which slowed me down for a while.''

That's hard to imagine. Given how far and how fast he's come, his career seems to have been run at full throttle. When I speak to him later in London, he has moved back to the UK and even talks of setting down roots. But the next day he's off on his travels again. He's agreed to do a small European independent movie in Croatia. He'll be there until October. And then on to the next thing. He says he's so busy he doesn't know what he's doing next half the time. The question is why. It doesn't sound as if money particularly motivates him, though I've heard he got a million dollars for one movie, not bad for a below-the-title actor. ''Who told you that? I've got no recollection of that.'' He has bought a house for his mother - a Christmas present - but that's the only indulgence he talks about.

The way he describes it work is just an alternative to drinking. The first time we spoke I hadn't realised how big a deal his brother's party had been. Not only was it his first drinking session for a year, when we speak again it has become the last. Yet there was a time when being drunk was his natural state. ''I hate sounding like one of these reformed holier-than-thou (characters), but it's a different world now and I do enjoy myself more. I appreciate my life more. I appreciate all the travelling and all the different countries, I really enjoy them now, whereas before it was staggering from airport to airport, sobering up, doing the film and then getting drunk again. Those days are over and I'm starting to smell the f-ing roses or whatever you call it.''

So the work fills up the added hours. ''That's the thing. I've got to fill my time somehow. This sober world is a bit boring; if you don't drink you've got to find something to occupy your mind.'' It's a plausible explanation as far as it goes, but only up to a point. It wasn't as if he wasn't working when he was drinking, after all.

Maybe the explanation is much simpler, banal even: he just likes the acting life. ''It's my job, it's a joy,' he agrees. ''It's the first time in my life that I'm doing anything I like doing. I go to work in the morning, I wake up and I go 'great, I'm going to work'.

For Tommy Flanagan, work is a four-letter word. Spelt l-o-v-e.

Trauma has its European premiere on Friday, August 20 at the Edinburgh International Film Festival. It goes on general release on August 27.