Probably the last occasion when a British comedy team broke into films with a fantasy spoof was the execrable Morons from Outer Space (1985) – not a good omen. Shaun of the Dead has ‘could go either way’ written all over it. Thankfully it’s eminently enjoyable, if never amounting to more than the exact sum of its parts. Ostensibly, it’s a comic take on George Romero’s modern zombie tales, transposed to contemporary down-at-heel London. Shaun (Pegg) is a no-mark stuck in a sales job, and getting no younger. His girlfriend Liz despairs of him, and the minute she kicks their relationship into touch, the undead start rising.

The whole project’s an offshoot of Channel 4’s ‘broken comedy’ hit Spaced (1999 – 2001), which also starred Pegg and was directed by Edgar Wright (who collaborates with Pegg as writer here). Shaun’s best mate Ed is played by Spaced regular Nick Frost, and Pegg’s TV co-star Jessica Stevenson bags a recurring cameo. Whereas the cine-literate sitcom was virtually assembled from a patchwork of film references, this lifts the classic zombie framework wholesale and treats it very faithfully. This leads to some intriguing blurry moments – cue scenes of pure weird drama that seem far closer to real Romero than My Family.

The real strong point here is the cast. The central double-act of Pegg and Frost are a treat to watch, full of neat nuances and throw-away lines. Other players read like a Who’s Who of the current British sitcom scene, from The Office’s Lucy Davies to Black Books’ Dylan Moran (as well as such familiar faces as Martin Freeman, Reece Shearsmith and Matt Lucas in silent cameos). The thespian side’s shored up by the ever-watchable Bill Nighy and Penelope Wilton, with the underrated Kate Ashfield shining in particular as the long-suffering Liz.

Somehow, though, it lets itself down rather. The tone of lost, aimless lives in the capital is fascinating, but it never has much bite – Romero’s own Dawn of the Dead (1978) is far more sharp and satirical. The zombie scenario here never generates much menace, comic or otherwise, and in all the laughs could do with being heartier and more frequent. (The gentle humour of Spaced seems lost in a darkened auditorium).

Nor does it entirely shake off the classic TV-talents-moving-into-film curse: the premise is thin and spindly, and seems stretched out at a hundred minutes. It’s rather too obviously the work of first-time film writers adhering slavishly to screenwriting wisdom, all clear-cut structures and ‘character journeys’, whereas a more brave, unexpected approach might have made more of an impact. In due course, great things may come from Pegg and Wright; certainly this is full of promise, and for now, at least it’s superior post-pub DVD fare – which is, essentially, what it’s aiming at being anyway. At the very, very least, it pisses all over Morons from Outer Space from a great height…