Directed by Stephen Frears. Starring Chiwetel Ejiofor, Audrey Tautou, Sergi López, Sophie Okonedo.

San-papiers is the French term for displaced people, who lacking the documents required to live in a country, spend much of their lives looking for the correct stamp on a piece of paper. 'Dirty Pretty Things' is set amongst the sans-papiers of London, who struggle in a seedy world of kitchens, sweatshops and cabstands.

Stephen Frears’ compassionate film cleverly avoids the trap of allowing a difficult subject matter to create a strident, preachy narrative. Instead the script (by 'Who Wants To Be A Millionaire?' creator Stephen Knight) is both a gruesome thriller and an "odd couple" romance.

The thriller elements are strong, and the gory details of the exploitation and villainy attached to the trade in fake passports is toe-curlingly tense and realistic, if a little contrived in its conclusion. The romantic narrative is less sure-footed, but the film comfortably succeeds nonetheless. The pace and atmosphere are just right, the tension is ratcheted up notch by notch and the performances are generally superb.

Chiwetel Ejiofor is excellent as the quietly desperate Nigerian, Okwe, exuding strength of character and charisma. Audrey Tautou convinces as Saney, the dreamy young Turkish immigrant who shares a flat with him. The supporting players, many of who did not speak English when the film was cast, all acquit themselves well.

Some of the supporting roles may have seen the screen a few times too many (Hooker with a heart of gold anyone?) and the hero seems almost too heroic for such a gritty environment, but it is impossible not to be drawn into the story. The film also occasionally surrenders to the weight of its politics. Ejiofor’s character Okwe offers a didactic, unnecessary monologue about his invisibility as an immigrant, rounded off with a painful joke.

The director is understandably reluctant to show too much human failure in his main characters. They are simply heroes or villains. The farcical demeanour of the immigration officials (refugees from TV's 'The Bill', by the looks of them) is a good example. Frears himself admits that these characterisations could have been better handled.

One of the strongest aspects of 'Dirty Pretty Things' is its setting – the murky London underworld, as previously glimpsed in movies like 'Mona Lisa' and 'Croupier'. This milieu is as strong a character as any in the script. Its rescue from the glossy wreckage of Guy Ritchie’s poppy-cockney is just one of the many good things in this entertaining and heartfelt film.

Luke McManus