A dark Manchester back-alley is witness to a violent rape by Johnny, intelligent out-of-work twenty-something who swiftly removes to London in a stolen car to visit erstwhile girlfriend Louise. Almost immediately he is stoned and bedding spaced-out flatmate Sophie before taking off on an ill-lit odyssey through the shabby streets with the flotsam of the capital: a brittle cafe waitress, a lonely would-be-reincarnated security guard, a pair of down-and-out Scots kids.

All have cause to remember the Mancunian, his acidic self-justification and bitter philosophising. Johnny hates everyone, himself most of all, singling out women for particular wrath; even sex with consenting partners, driven by misogyny, is invariably cruel and rough. The merest compassion or civility is met with harsh sarcasm or else spirals off on bizarre, ornate streams of consciousness at the drop of a hat, anything from The Bible and astronomy to barcodes and apocalypse.

As Johnny, actor David Thewlis took Best Actor at Cannes, and it's a performance that commands a vice-like grip on the audience without once resorting to easy tricks; even hints of a possible redemption are chillingly faced in the final moments with no let up.

Leigh's reputation for the social comedy of Abigail's Party or Life Is Sweet means the laughs come aplenty in Naked, albeit early in the picture when Johnny's casual malice possesses a certain comedic flair. But, shot on recognisable, unsanitised locations in Dalston and Soho, it becomes a progressively blacker portrait of a convincingly heartless London. Encounters with the homeless kids or rambling, cod-philosophical discussion with night-watchman Peter Wight are equally hilarious and tragic, inner-city decay and the waste of lives fuelling a rage that ultimately, almost randomly, is physically revisited.

The rather un-English direction (another Cannes winner) is unobtrusively cinematic and Leigh is served by almost flawless ensemble playing - Leslie Sharp's Louse is exhausted by Johnny's extremes but, knowing of his unilluminated Northern past, is not altogether unsympathetic; Claire Skinner is the practical third flat-sharer driven to neurotic distraction; and Katrin Cartlidge takes Sophie from druggy lethargy to victim with formidable ease.

Greg Cruttwell's yuppie landlord, Jeremy, is the only real hurdle, looking to have stumbled in from some other, rather less insistent Leigh piece. His sexual power-trips mirror Johnny's but in crudely stereotypical brush-strokes that push the film over the dangerous two hour mark, much to its detriment.

Minor reservations aside, few would deny the sheer verve and ambition of Naked. Even post-Goodfellas the violence of language here retains a capacity to shock, and the mundane quality of the setting serves only to remind audiences that this is very much contemporary film-making. For its scope, central moral ambiguity, and particularly for the electrifying performance from Thewlis, this is that rarest of birds, an essential British film.