The invisible Londoners

Stephen Frears is a director unlike most who work in Britain (or, indeed, outside it). He is a film-maker with something to say. Dirty Pretty Things, to its credit and our film industry's shame, is almost the only British-made movie this year that tells us how our nation is changing.

Not before our eyes, though. The parallel world of illegal immigrants that Steve Knight's screenplay collects is the one most of us who move around London don't see. It's a thriller that happens within the underclass of desperate people from half a dozen countries attempting to keep on one side of the law, or the other, as day turns into night and back. This is a London we nativeborn Brits used to say "belongs to us". It belongs to no one now. Every character, those enduring exploitation as well as those employing it, represents the polyglot, multicultural population existing below eyelevel in the capital. Most are illegally working in jobs the Brits won't do.

As the film's awkward title suggests, they make the dirty things that other people do look pretty in the morning. All exist at the mercy of insecurity and imminent discovery. It's an unsettling film, also a gripping one. It tests its cast to ring true against what we know to be the daily reality of asylum seekers. Most pass, even the least likely one, like Audrey Tautou. The recent star of the French comedy Amèlie, who always looked sunnyside-up and made heaven move to bring lovers together, comes down to earth with a bump of raw reality. She plays Senay, a Turkish room-maid working in a florid Shoreditch hotel. An economic migrant - "I didn't want to live like my mother" - she's no longer fey, but spitfire. Those famous eyes that seemed twice as large as nature intended burn with determination to survive amid the ethnic underclass swilling around London's cracked old mixing bowl.

But the central figure of the film, and an actor who emerges to full cinematic stature, is Chiwetel Ejiofor. With the physical charisma of Samuel L Jackson, and none of the US star's self-regarding machismo, Ejiofor plays Okwe, a Nigerian "illegal"-who trained as a doctor back home. Now he drives a London minicab by day, treats fellow drivers for VD, catnaps on Senay's sofa while she's at work, chews herb to keep his energy up, then dons a night porter's uniform at the Hotel Baltic. Summoned to rectify the plumbing, his hand fishes an unlikely blockage out of the lavatory: a human heart.

What's going on here? Gradually, he uncovers an illegal trade in body organs, the "currency" of survival among immigrants. A kidney buys a passport for a family. In one scene that summarises this displacement of hope and humanity, a Somali in pain after botched surgery has to depend on his child to explain his condition - the boy is the only family member who speaks English.

Okwe traces the racket back to his hotel's Spanish manager, nicknamed Sneaky. Played by Sergi LÛpez, the sinister "friend" in the Hitchcockian thriller Harry, He's Here to Help, LÛpez delivers a masterly performance-of impermeable inhumanity: no warmth seeps through this born entrepreneur, who summons folk to do his bidding with a whistle as imperious as a car bleeper.

Okwe draws on the assorted nationalities among his friends to end his game in a way that makes one flinch at the callous tit-for-tat involved. It frees him and Senay to go their separate ways. Their plot doesn't have to be entirely plausible to make its point, which is the multiethnic free market in survival favours that the film's underclass has established. There's the Chinese porter (Benedict Wong) in the hospital crematorium who offers the homeless a bed for the night on a mortuary slab; the Afro-Caribbean hooker (Sophie Okonedo) who bravely furnishes sexual bait; the Balkan night-watchman (Zlatko Buric) who dominates the lobby like a hairy Goliath. A telling scene occurs in an illicit rag-trade sweatshop that empties quicker than you could cut a cotton thread at the sound of a police siren. There, Tautou sinks her teeth into the sensitive parts of the Pakistani foreman (Barber Ali), then runs for all she's worth to keep a jump ahead of the immigration enforcement officers.

If the film has a serious flaw, it's the caricaturing of these rotweiller officials. It would have gained even more urgency had it taken the measure of Britain's asylum-seeking inflow - 22,500 in three months this year - from the efforts of those monitoring it. But the populous mix of characters and events leaves little space for fine shading, while the threat to society is subsumed by the emotional crisis of individuals.

Dirty Pretty Things is photographed by Chris Menges, who draws out the essence of a place rather than the geography of a location; designed (in a way you'd hardly notice) by Hugo Luczyc-Wyhowski; and edited with economy by Mick Audsley. All three have been on Frears's workforce before. The director himself, since he and Hanif Kureishi first explored Britain's ethnic communities in the Eighties with My Beautiful Laundrette and Sammy and Rosie Get Laid, has established himself in the front rank of film-makers who can illuminate while entertaining.

This film will make unsettling viewing for white Anglo-Saxon Brits, seeing "their" metropolis as a sort of illegal "jobs centre" for an underclass whose readiness to accept any dirty job may lead to a Helot economy and compromise irretrievably the meaning of national identity. But simply to say that Dirty Pretty Things possesses this political dimension makes it a valuable film in the debilitated state to which indiscriminate cultural subsidies dished out by the incompetent to the untalented have reduced the British film industry. Here at last is a movie with a social heartbeat that pumps new blood into our anaemic cinema.

Dirty Pretty Things
Cert: 15