JUAN CARLOS FRESNADILLO'S new film 28 Weeks Later stars the English . . . that most normally civilised of people . . . as a rampaging horde of brutes. They run about in a frenzy: they gather outside a building in large numbers and will do anything to get inside. Doors are smashed, windows are broken, and those who can't get in bang their heads in frustration. What is the panic? Is there a new Ikea store opening in town? No, it's another outbreak of Rage virus . . . the infectious disease that turned Britain into a population of flesh-eating zombies in Danny Boyle's 2002 horror film 28 Days Later. And Spaniard Juan Carlos Fresnadillo, who directed the classy arthouse thriller Intacto, returns to apocalyptic England to pick up where Boyle's film left off.

He sinks his teeth into the genre.

As sequels go, I was not expecting this: the film delivers horror, gore and zombies that come lurching out of the shadows with the same manic terror of that first film . . . one of its great features was the way its zombies could run as fast as you can. But Fresnadillo frames it with arty panache, and the same style of fraught digital camera work that was a signature of the previous film. And he slips in a sneaky, subversive edge, highly-enjoyable and in the tradition of zombie supremo George A Romero, which turns the film into a commentary about the fallacy of military containment and the US occupation of Iraq.

Robert Carlyle, in full actorly mode, plays Don, a soft-spoken man whose kids had been sent abroad before the outbreak. We first see him abandoning his wife Alice (Catherine McCormack) to the fate of zombie snackfood after she hesitates while fleeing a hideout. The film then skips to London seven months later where Don is reunited with his children Tammy and Andy (Imogen Poots and Mackintosh Muggleton). A section of the city has been cordoned-off and is being repopulated by US-led Nato forces. It's called the Green Zone. Sniper posts are on every building. The rest of Britain is a wasteland but the Americans are confident they can contain an outbreak should it occur again.

The kids repay the Americans' efforts by slipping out of the secure area . . . an act expressly forbidden . . . to visit the family home in the vacant suburbs and get some things: a family photograph, personal belongings and a mother who was supposed to be dead but is now found hiding in the attic. The Americans stick her in quarantine: it emerges she is genetically predisposed to carrying the virus but is not affected by it . . . so this means her children could be too. Then Don, remorseful for leaving her behind, sneaks past security to visit her and plants a big kiss on her lips.

Whoops apocalypse!

Much of the plot hinges on the illogical and the convenient . . . just how many doors in a secure zone go unlocked? And Robert Carlyle keeps turning up when really he should have gnashed his way offscreen long ago, as if to justify his expensive cheque. But there is a crude logic to how the virus is passed on . . . human stupidity. And it revels in this comedy of errors.

As the virus spreads, the Americans panic and lock everybody up. But there is somebody inside with the virus and those in the warehouse, blanketed in darkness, begin to turn on themselves.

The doors burst open . . . how do you tell who is infected and who is not? So orders are given to open fire on everybody. It's a bloodbath straight off the Odessa Steps in Eisenstein's Battleship Potemkin . . .

but here the innocents have to dodge hungry zombies and American bullets too.

Soon Code Red is invoked which means London is firebombed and everyone incinerated. The kids, in the care of a US military doctor who believes that within them lies an antidote, tries to get them out of the path of the Americans who are zapping everyone with flamethrowers. It's a neat trick:

suddenly the US military, and not just the zombies, are the villains despite that they are doing their job. You find yourself rooting for the kids, slotting to the back of your mind the suspicion that one of them is now a carrier. It's an entertaining way of playing politics with a dumb genre and it is sure to resonate with what you see nightly on your TV set. Watching it unfold in central London, vast and empty, instead of a faraway place, gives the film a whole other dimension of horror. It seems to say: just how do you like it now?