What has earned Thewlis all of this attention is, of course, Naked, the film in which he starred. The actor spent seven months researching and performing the part of Johnny and one critic compared him to Vlad the Impaler, another to a verbal Jack the Ripper. He says that living the character was heaven and hell. "To be allowed to attack people verbally-viciously-lay into people, it's so liberating. It's like being sick."

Thewlis became increasingly addicted to the feeling. He says the scene at the climax of the film, where Johnny scrabbles around at the top of the stairs, out of control, was, "More or less real, that's how I felt-raging." He says, "You have to address the question-what's the meaning of life-but I was asking it every day. Everything in life was called into question. I ate very little in order to stay wired and spent all of my time reading or smoking. I became obsessed with death and kept thinking I was having a heart attacks. I was so freaked out, so distressed-I couldn't sleep."

I asked if he's seen Hearts of Darkness, the documentary about the making of Apocalypse Now. When we see Martin Sheen in one scene clearly undergoing some sort of breakdown (he went on to have a heart attack), we hear Coppolla declaring that Sheen's well being is less important than an authentic performance and the success of the film. Thewlis says: "Yeah, a friend recommended that I see that film. I related to that so much-I can't tell you. What Coppolla was doing to him, Mike was doing to me. I felt like, 'I know, I know'. You feel like swearing at him. Obviously it was a bit more extreme for Sheen. But I felt, 'what are you doing to me. Why are you pushing me this far. I've had enough.' It's only a film. But that's what it required. I couldn't have done the part without getting involved." His anger toward Leigh quite evaporating, he says, "I'm alright now. It was worth it. You have to do things physically to acheive the state of the character. If my character was an alcoholic, a drug addict, I would do that." Mike Leigh was not uninvolved in his stars' crisis. He sent Thewlis to the morgue to look at dead bodies and Thewlis says: "He wanted to compound my fear of death, not that it needed to be compounded. I was already pretty scared of death without going to see corpses." He asked only that he not be shown the body of a woman or child. In the event, the body he was shown was that of a 12 year old girl.

Thewlis began to sleep-walk and one night wouldn't let his wife into their flat. She rang him from a call box and when he picked up the phone he found himseld making strange grunting noises. She thought he was having a heart attack and called the police, who broke down the door with an axe. He admits he's still feeling the effects of Johnny. The other day, when two men were looking at him in the street, he hissed, "What are you looking at? I'm not a fucking monkey in a cage." (I make a panicked mental note not to look too starstruck!) He says he wouldn't take a part like that again. "It's not healthy. I got too involved. At the end of the day, the meaning of life is the only thing worth thinking about. Why do we need to talk? Why has it all become so bizarre? Sometimes I just can't think of anything better to think about."

He has read upon on the ecological suicide the West has embarked on, but doesn't want to go on about it. He says of Johnny, but it seems equally true of himself, that "I didn't want him to become David Ike." He may dress better than Ike, but he is clearly haunted. Thewlis said the thing that would improve his life would be if there was a god who would come down and say everything's going to be alright. He has become interested in Buddhism with its focus on individual responsibility. "We must believe in, we must love, anything which isn't capable of looking after us. If people hit us, we've got to forgive them." Warming to this theme, he says he has often thought people were devolving. "we have to talk, write things down, indulge ourselves, to cope with life."

For his latest film, Restoration, Thewlis plays a Quaker and says he thinks Quakerism is the coolest Western religion-"just meetings, meditation." To get into the character he is going to try giving up smoking, drinking, and impure food. He also wants to give celibacy a go. He admits that he's tried abstinence before and that after three or four days of "feeling great, it started to inhibit me- suppress me-and made me anxious again all over. Personally, I've realised that often in life your decisions are sexual ones. You are attracted towards someone, they might not be the ideal person-but you get involved. There are responsibilities. If you judged objectively you wouldn't choose them. I'm starting to sound like a stoned student."

One release he has always found is art and it sounds like this is his one, real religion. He says what makes him tick is writing and painting. "When I go to bed, if I've done that creative release there isn't a better feeling. Even if I get up in the morning and it's shit." His drawings, apparently, aren't light and airy. He says he draws and doodles a lot of faces, which often turn out to be terrifying.

"Because of what's happened-success in a commercial way-one of the things that really winds me up is that I don't have time to do what I want. I'm involved in so much, it's a compromise." Acting, he says, doesn't give him enough control. He wants to write screenplays but worries that producers would mess around with his ideas. He is currently working on a stage play in which an artist is driven insane by his own paintings. The artist leaves a painting at the door and the faces he has created are so disturbing that he can't get out of the studio. The parallel is meant to be obvious: the pure and sensitive artist suffers for nothing-his nightmare irrelevant to the world.