The only uncertain thing about this film is whether it takes the slightly one-joke premise too far or not. Like similar ideas in film (Dead Snow, Lesbian Vampire Killers), these things lend themselves far more to short sketches, and if you intend for your Nazi/zombie/dinosaur/robot/ninja/etc comedy to be more than an hour long you need more than just the joke premise.

The first promising element is the running time. At 88 minutes it's just long enough to include gags, exploding zombie brains and action but too short to believe in itself too much and end up too self important.

There are a couple of brief setups, and we're off. Two construction workers find an old, sealed up chamber beneath a site in London's East End somewhere, and when they open it up hoping to find centuries-old treasure they instead let its undead occupants out, setting off a zombie apocalypse.

At the same time, hapless brothers Terry (Rasmus Hardicker) and Andy (Harry Treadaway) are putting the finishing touches on a planned bank robbery they want to stage to raise the money to save their beloved grandad's rest home from redevelopers.

Along with their tough cousin Katy (Michelle Ryan), sad sack Davey and insane war veteran Mental Mickey, they set off. But as the hordes start to spread across the city, attacking and turning Londoners everywhere, the gang has a much easier time of escaping than they realised – even after someone's raised the alarm – because all the waiting cops outside have been attacked by the living dead.

They take two bank workers hostage anyway and make for the safe house, battling their way through the flesh eating hordes to try and decide what to do next.

Meanwhile, zombies have reached the rest home where the residents, led by the boys' grandad Ray (Alan Ford) – a very hard local and probable former gangster (although I might just be recalling Ford's immortal role in Snatch) – has to lock all the doors and try to hold them off.

There are a few clever jokes, like the one where one resident who's been caught napping in the garden has to race a zombie to the back door so as to not get eaten – the world's slowest foot race, owing to the zombies' shuffling gait and the old man being on a walker.

But most of it's what you're hoping for and to some extent expecting, no more and no less, pitching itself perfectly in the middle of funny vs scary, gory vs sanitised and satirical vs narrative.

Even though the acting is overcooked on more than one occasion, there's enough blood and action to keep you entertained and yes, that is the same Honor Blackman (playing rest home resident Peggy) who played Pussy Galore back in Goldfinger.