That desire for home permeates 'Naked', a picaresque chronicle of spiritual homelessness whose cast also includes such rising British actresses as Lesley Sharp and Claire Skinner, playing two London roommates with whom Johnny seeks refuge. At Cannes this year, the film, Mr. Leigh's first feature since 'Life is Sweet' in 1990, won awards for best director and best actor and went on to acclaim in October at the New York Film Festival.

Yet, as shaped by Mr. Thewlis in a performance Vincent Canby in the Times said was 'staggeringly fine', the movie is as different from 'Life is Sweet' and High Hopes' (1988) as it is possible to be. Those films were ensemble pieces whose unironic titles allowed light into life's dark tunnel, but 'Naked' places its virtuosic leading man on a relentless 'via dolorosa'. Beginning with a sexual assault in a north of England back alley, the film moves to London to follow Johnny's spiraling descent into casual cruelty and no less casual sex --- a milieu enriched by his way with words.

Johnny is both charming and dangerous, self-destructive and self-aware, as he goes his scruffy way quoting Nostradamus and Revelations like some wide-eyed Satanic jester. Capable of rape in Manchester one minute, he is the rapier wit of East London the next, joking about the 'halitosis chorus' even as he sinks into the 'fistula' of the British capital, which is to him what James Joyce's Dublin was to Leopold Bloom.

The gangly and engaging Mr. Thewlis shares Johnny's love of language, an unsurprising attribute, given Mr. Leigh's well-known habit of building his movies from his actors' improvisations. And if Johnny's danger, happily, is nowhere in evidence over lunch with Mr. Thewlis, it hovers by association. 'As long as you're in character,' Mr. Thewlis said of Mr. Leigh's working methods, 'anything can happen.' Surveying his plate of tortelloni, Mr. Thewlis imagined Johnny upending it into a journalist's face. 'It's not in the character of me to do it,' he said. 'But if I was Johnny in this restaurant now, it would be a different scene.'

If Johnny is contradictory, well, then, so is the world around him; God may be absent, but so is reason, which makes Johnny only that much more determined to rage recklessly, and sometimes humorously, into the bleak night. (Asked whether he has ever seen a dead body, Johnny replies, 'Only my own.')

'People come out of this movie very confused,' said Mr. Thewlis. 'The guy violates women; he violates people. He only destroys. The only thing he creates with this intellect and his wit is a weapon of destruction which therefore cancels itself out.'

Still, the actor continued: 'Everybody knows someone like that: wonderful, attractive people full of passion and ideals. You envy them, but you know there's a dark side, which is brutal and cruel and violent. That dark side informs what's wonderful about them, and the passion and rage inform the darkness; they're inseparable.

Mr. Thewlis's own contribution to 'Naked' is not less essential to the movie. Like all of Mr. Leigh's work, the production began with nothing more than a cast, all of whom were kept from one another until it was time to meet in character. With Mr. Leigh's encouragement, Mr. Thewlis went on to immerse himself in the literature that might have formed Johnny's largely bleak world view, from Leibniz, Schopenhauer and Spinoza to Mao Zedong and Stephen Hawking's 'A Brief History of Time.'

While Mr. Thewlis was not without doubts during filming -- 'Some days, I'd get terrible paranoia and think, 'Johnny's just too much to put in into a movie; people won't tolerate it' -- Mr. Leigh had faith in an actor with whom he had worked twice before (in 'Life is Sweet' and in his brief 1987 film, 'The Short and Curlies'). 'The general assumption I make', said the director, 'is that I will push each actor quite to the hilt and exploit them as much as I can. I knew David could hack it with the reading and bring to it much brainpower.'

Mr. Thewlis more or less fell into his career. The middle child of Blackpool shopkeepers, he decided in the late 70's to accompany two musician friends to London to auditions for the Guildhall School of Music and Drama -- and was amazed when they all got in. ('I wanted to keep the band together, so I thought I'll apply,' he said with a laugh.) Until 'Naked', his career was the standard English actor's mix of London and regional theater -- Edward Bond's 'Sea' and Michael Cristofer's 'Lady and the Clarinet', among other plays -- and film and television work. (Mr. Thewlis is a guard in the opening moments of Harold Pinter's current screen adaptation of 'The Trial'.)

Next summer, Mr. Thewlis will be seen in Warner Brothers' new version of 'Black Beauty', playing the tubercular cockney cabbie who brings Black Beauty to London. The film's writer- director, Caroline Thompson, agreed that it might seem odd to ask a misogynist to play a sweet cab driver, but in the end, Mr. Thewlis's eyes did it: 'They're huge', said Ms. Thompson, 'and have this clarity and honesty about them.'

But one collaboration between Mr. Thewlis and Mr. Leigh, a stage 'Hamlet', seems unlikely. 'It will remain a fantasy' said Mr. Thewlis, aware that 'Naked' has taken its place. 'In a way, I think that this is Mike's 'Hamlet'; we've pretty much done it.'