Actors don't have much control over what the end product is. You hand yourself over to these people. Sometimes it's wonderful. Sometimes it's The Island of Dr Moreau." David Thewlis is back in Cannes for the first time since he won a Best Actor award here four years ago for Mike Leigh's Naked. He's done six films since then and is disarmingly critical about most of them. "If I said they were all great," he comments, "I'd look a real tosser."

Definitely no tosser, Thewlis checks the movies off, one by one. "Well, The Island of Dr Moreau wasn't very good, was it? I remember the day Brando turned round to me and said this was the craziest thing he'd ever been involved in. And I thought, if this is the craziest thing Brando has been involved in, then fuck me...

"Restoration I did because I really loved the novel and I like Michael Hoffman, who directed it, but it wasn't a really challenging part for me. I'm not critical of the film: I just don't think I gave a very interesting performance.

"Then I did Dragonheart because I was getting advice-stroke-pressure from my agent to do a studio film. Actually, I enjoyed doing it. It wasn't the greatest script in the world, but not many people can say they've played a wicked king in a swashbuckling Arthurian special-effects monster movie. I've only seen the finished thing on an aeroplane, so I don't really have an opinion as to what the end product is like."

And Total Eclipse? "I did that after Dragonheart, thinking that had been a bit Hollywood and not really where I wanted to go. It was actually the thing that I've put my heart into the most, in terms of research and everything, because I was a great admirer of Rimbaud's work. Still am. But, er, the film wasn't very well received, was it?

"I suppose there was a disparity between Leonardo and me, especially in terms of accent, which I think jars a little. We weren't going to do 'French' accents, because Agnieszka didn't want that. At one stage, there was talk of doing a mid-Atlantic accent, whatever the fuck that is. Underwater, maybe. "But then I thought, if Verlaine had been English, he would have been a contemporary of Tennyson - an upper-middle-class, literate, educated man, living in the capital, so I did that kind of accent. And Leonardo... Well, Leonardo did what he did, you know? I like him and I tnk he's a very good actor, but I don't think anyone was cast right in that film. I don't dislike it myself. I'm actually quite fond of it."

As for Thewlis' presence in Cannes, Gilles Jacob flew him down at the weekend - private jet from "some airfield in Middlesex", helicopter from Nice to Cannes, into the designer gear with all the young British stars, up the steps of the Palais. Frocks and film. It was one of the less obvious of the 50th anniversary ideas. Jacob himself didn't show up (a festival crisis, apparently), but Thewlis doesn't seem to mind. And anyway, he's long out of the designer stuff, back into baggy black pants and sturdy, seriously scuffed boots. His head was shaved for Seven Years in Tibet - or 'Five Years on This Set', as the crew called it - but the hair is beginning to grow back.

Thewlis has done that, plus American Perfekt, which is showing in Un Certain Regard today, and a one-day cameo - "Well, more of a very small part, really" - in the Coen Brothers' The Big Lebowski. "I met the Coens here a few years ago and they said they liked my work. I said I liked theirs, so we said: 'Let's work together.' Then Brad [Pitt]'s make-up artist on Seven Years in Tibet always works with Joel and Ethan. She left the picture early, and I said, 'Will you remind them that I want a part in your movie?' "They said, 'Steve Buscemi's doing a day on it and John Turturro's doing a day on it. Do you want to play this little part?' Hopefully, they'll give me a bigger part next time because of all the filmmakers in America, I'd like to work with those two the most." They also taught him how to do conjuring tricks for the part but, pressed, he bottles out with "I haven't got me props. You need props for prestidigitation." He makes convincing movements with his fingers. "Have you got a half dollar? No? A ten-franc piece is too small. Can't do it."

And American Perfekt? "The director and writer, Paul Chart, is maybe my best friend in Los Angeles - an English guy living in LA who came to me a few years ago with this script called Headcase. I didn't read it for a long time because I was getting all these bigger scripts and this one looked really dog-eared, you know? "Then, when I finally read it, it was the best thing I've read for years. All kinds of things came and went and it didn't happen. But I became good friends with Paul. It's sort of a dark comedy road movie shot in the Mojave desert with a very small crew, and I'm one of the oddball characters along the way. "I did it purely for fun. I haven't seen it, but I'm pretty sure I'm going to like it because it wasn't like the other ones. It was like making a film with friends. "Paul is one of the most passionate people I've ever met in terms of the art of film. We have about six scripts ready to do in the future, which hopefully I will do with him. Also, I wanted to work with Fairuza [Balk] again because I think we want to exorcise the memory of Dr Moreau and do something good together."