You can tell what Jerwood Space is like from the name. A heavily designed, not quite-finished arts facility in suddenly interesting Southwark. A little piece of Hoxton parachuted across the water into enemy territory: glass, pale wood, plenty of ciabatta and polenta in the cafeteria, but no Diet Coke, and it's a Diet Coke Dougray Scott wants, as well as a cigarette or five, in his strictly timed one-hour lunch break. Hey, perhaps he should send someone out for a can, seeing as how he's such a big hotshot Hollywood star and everything?

'Ha ha ha! Um, it doesn't really work like that,' he laughs uncertainly.

'I'll be all right, I think! Ha!'

'Yes, of course it makes me nervous! Absolutely. Of course it makes me nervous, but I'm in good company. I mean, I'm being led by one of the best directors in the business. And Sam, Sam is very confidence-inspiring...'

For someone who's basically very cagey, Scott is marvellously open and chatty. More than happy to discuss the nuts and bolts of his career at length, he's endearingly bashful about his status as 'the new Jude Law', and neatly deflects any attempt to get under his skin by unpicking the question itself and declaring it invalid. 'Why would anyone want to know about my childhood?' he asks. 'What's important is whether I'm any good. I'm interested in talking about the work, I understand that people might want to know about that. But all the other stuff I find bizarre. I find it intrusive.'

His childhood in Fife, though, is the one thing he will tell you about - or rather, he will tell you all about his father, a heroic figure by his son's account, who kept his family together in the face of hardship, lived his life with enviable gusto, and must have been a hard act to follow. 'My father was very inspiring to me as a human being. He was a salesman at the end of his career, and a lot of being a salesman is covering up what you're actually feeling inside, giving the impression that you're really enthusiastic. It was a performance every time he went out. But he did it. Not very successfully at all, he didn't make a lot of money. But he was a glorious man, my father.'   Scott senior could be pretty cagey too. 'My father was an actor for six years. He was in the Unity Theatre, which was a socialist theatre in Glasgow, after WWII, but I didn't know about that until I was 16, 17. He just never talked about it.'

Scott doesn't seem to think that this is weird. And he makes it clear that any suggestion that he's following in his father's footsteps is on very shaky ground. 'I'd already made up my mind,' he says. 'No, the thing that my father did that I really wanted to do was football. He was a footballer in 1936, he was at Queen's Park. He was good. Rightwinger, really fast. But then he got caught up in WWII, and then he was... loads of things. Then he was a copy boy on the Daily Express. And then he was an actor, and then he sold sausage skins for his uncle. He just tried different things, but in the end he was happy doing the job that earned him the least amount of money, being a salesman. Because there was no stress.'

When his father died four years ago, Scott's career was still in its early stages. But, having established himself as a television actor, he decided he couldn't share his dad's path-of-least-resistance philosophy; a mixture of confidence in his talent and a certain gung-ho attitude dictated that he play for higher stakes. The turning point was when he left the 'very frustrating' 'Soldier, Soldier' to appear in 'Twin Town', Kevin Allen's bumpy but interesting debut. Scott's powerful portrayal of a seedy, bent cop was generally agreed to be the best thing in the film, and opened the magic door to international stardom.

'Yeah, and "Twin Town" is the film that still gets me in,' he adds fondly. 'Because in America, people in the industry loved it. I still love it.'  As he puts it: 'l never went after Hollywood, it happened because they came after me.'  His first Tinseltown gig, 'Ever After', in which he smouldered beautifully as a fairy-tale prince, won hearts among the housewives of America, but it was 'MI-2' which established him as genuine hot property. He did the film 'for a laugh - and for the money', but he hasn't come this far to settle for life as the British rent-a-baddie in a string of action films.

In this context, 'To the Green Fields and Beyond' is an excellent tactical move: a high-profile, serious production that's bound to add clout to his CV. Ever the son of a salesman, his enthusiasm is palpable. 'It's very different from the historical remembrance of the war,' he says, 'which is all about the innocence and the mud, the death and the youth and the blind leading the blind and how tragic it was - it was. But it was also a very, very futuristic war. It had all kinds of weaponry which had never been seen before, and it was planned, incredibly well planned, and there's something my character finds optimistic about that."

And he's fine, really fine, except that the generalised insecurity that seems to dog actors has this time coalesced around the fact that he's had so little time to prepare for the role. For the first time, he's had to cram a process which normally takes him several months into two short weeks.

'Acting gives me an opportunity to explore other peoples lives, and I feel that the research helps me in my understanding,' he says. 'It kind of gives you ammunition, and... a well of emotion, and memory. There's an organic thing for me: I get a sense of satisfaction if I can get to a point where I understand somebody else's life. Moments like that give you a sense of achievement. That's what my life is. I'm an actor. It may seem irrelevant to other people, who think acting is something that's not that important - and they're right, it's not that important. But it's something that gives me some sort of joy. A lot of people think the pleasure you get from it is from the adulation, being recognised, the doors it opens for you because of your fame, but that's not where my joy comes from. My joy comes from cracking a character or getting a scene right.'

He's makes it look easy, the leap from Hollywood Hills and Sunset Strip to Jerwood Space and Donmar Warehouse. 'I'm not saying I'm coming back to the stage because that's where the real acting is, and that's what you have to do to get your kudos. That's not why I'm going back to the stage. The reason I'm doing this is that it's a wonderful play. I don't feel I've got anything to prove.'

Not to the theatre fraternity, at any rate. Why, somebody has already appeared with a can of Diet Coke for the big man.