A little bit sour, a little bit sweet, Thewlis's disdain for fame would be a shtick if he weren't so impressively, and painfully, intent on being "himself". In his latest film, Divorcing Jack, a comic thriller set in Northern Ireland, he is as skinny, tight-trousered (and irresistible to women) as a pop star. But today, the 35-year-old's rubbery face is almost chubby and he wears voluminous pants. He's also stooped and twisted with back pain. Like a convalescent, he moves his cigarette to and from the ashtray as if carrying a breakable object. The man does not want to look like a star, and nor does he.
In fact, he's not even sure he likes acting any more. He thinks it's a "bizarre, sometimes grotesque" thing to do. Of course, in terms of plugging himself and his film, this presents something of a problem. He does express quiet satisfaction with the Northern Irish accent he managed to perfect (he has a thing about accents, you see; he was appalled by Leonardo DiCaprio's "Santa Monica" accent in the film they made together about Verlaine and Rimbaud, Total Eclipse). And, obviously determined to be positive, declares that with Divorcing Jack he "had a really good time. It's only when you've not done acting for a while that it seems bizarre. When you're actually there doing it..." But then he stops and shakes his head. "Actually I find it bizarre right in the middle of a take; I'm like, `What the fuck am I doing? Who are all these people?'"
I believe him, because there is something odd about his Divorcing Jack performance. It's as if he is taking deep breaths before the big lines, willing himself to become re-absorbed.
So what happened? Why has acting, for Thewlis, become so problematic? One thing that strikes me, during the interview, is how often his ranting chatter turns to The Island of Doctor Moreau, a film he made two years ago, co-starring Marlon Brando and Val Kilmer. Most of the talk concerns the film's director, John Frankenheimer. "I've got to be careful not to be libellous," he says with a grin, "but the director was an arsehole," [he looks at the tape recorder] and with a snort, adds, "in my opinion. It's all right to say that as long as you say it's just an opinion".
But Frankenheimer's 1962 thriller The Manchurian Candidate was so good... Thewlis shakes his head once more. "I can only think he had a lot of great people around him then, or his brain has become absolutely pickled since."
Such bile makes more sense when you discover that, during the four months on set, Thewlis almost had a breakdown. And he does make the atmosphere sound hellish - a slow, sickening stumble into chaos. Thewlis's anarchic humour hides a deeply serious side - he was desperate for order to be imposed.
"Frankenheimer would get me in his trailer," recalls Thewlis, "and say, `I'm gonna shoot the hell out of this because I don't know what the hell I'm doing'. I was like, `Don't tell me! I need you to say you're totally in control and that this is all going to be OK'."
Half of me wants to get back to Divorcing Jack; the other half is fascinated. Because what it reminds me of is the first time I interviewed Thewlis. That was in 1994 and, talking to me then, Thewlis admitted that Naked had been a nightmare ("I kept thinking I was having heart attacks"); that his relationship with Leigh had become fraught and all but caused him to have a breakdown. He compared himself to Martin Sheen during the making of Apocalypse Now, as exposed in the documentary by George Hickenlooper, Hearts of Darkness. Sheen went on to have a real-life heart attack. "I related to that so much. What Coppola was doing to him, Mike was doing to me." When Thewlis talks about The Island of Doctor Moreau, it's that same plaintive note of bafflement and injury you hear. The fact that Brando was on board was merely another, macabre link. And, like Sheen, Thewlis once again found himself torn. "There were too many dark psychologies clashing," he admits. "On Marlon's part there was disrespect for Val..." Thewlis tried thinking his way out of the hole. Thewlis and Kilmer began working on a new script. "We thought we'd do it as this Bunuelesque, surreal fantasy. It was the only way out."
And this is what's missing from Divorcing Jack. The part Thewlis plays, that of a scamp journalist, Dan Starkey, has all the actor's cruel, cynical wit and sensuality, but none of the vulnerability - the desire to be good, to take responsibility, to choose work over pleasure. Without that, Starkey is simply a male fantasy figure, a parody of Thewlis himself.
But back to The Island of Doctor Moreau, which Thewlis, having twisted and stretched his aching back, is still talking about. When he realised there was nothing he could do, he just wanted to escape. "I broke my leg in the middle of the film and I thought "that'll do it!" but they just dosed me up with pain killers and got a good double on." You begin to see, now, why the process of acting itself has been tarnished. The fact that Naked was a good film and The Island of Dr Moreau a ludicrous flop doesn't matter. Both made him prey to the confusion of others - to a loss of control and meaning. His solution: a change of scene. "I had a relationship there at the time, but I decided to leave." He puts his hands together, as if in prayer. "It was like `I'm going home'."
And what will Hollywood and the likes of Michelle Pfeiffer do without him? He doubts he will be missed. "You become judged entirely on your ability to bring in the dollars and the fact that none of the films I did was a huge hit became significant." There is regret in his voice, but relief too.
Thewlis's performance in Divorcing Jack, then, is a bizarre declaration of intent. He can still turn it on (his cameo in the Coen Brothers' The Big Lebowski was superb) but, accidentally on purpose, he is not a natural actor any more. It is writing, and possibly directing, that he believes in now. Talking to Thewlis about acting is like talking to a priest who has lost his faith - only when he talks about his script and, most especially, his new novel, does the evangelism return. But he is such a fragile body. God know what will happen if that fails him too.