One morning, as David Brent was waking up from anxious dreams, he discovered that in bed he had been transformed into a monstrous verminous prawn. That, at least, is the premise of District 9, the rather confused debut feature from Neil Blomkamp, who co-scripted the film with Terri Tatchell.

OK, so it’s not David Brent really, but I’m sure I can’t have been the only person to have found the early scenes of the film comically akin to The Office, and its protagonist Wikus Van De Merwe to share some of the hapless self-absorbed Brent’s characteristics. Only, Wikus works for a multinational company big in the weapons trade rather than a stationery supplier. And his job brings him into contact with an alien race, nicknamed prawns, who for no readily apparent reason flew their ginormous spaceship to Johannesburg 20 years ago, and have been living in a shanty town every since.

All this is revealed through news footage, which is good in that it gives the film a raw feel that’s to its advantage when the aliens appear. And bad since it allows Blomkamp to get across all manner of exposition through reportage, rather than use more inventive and less obtrusive means of layering the story.

Ah, the story. OK, initially Wikus is involved in relocating the aliens from District 9 to a pupose-built camp — you’d be right in suspecting some racial theme going on here fitting in with South Africa’s apartheid past, though it isn’t explored particularly. What matters is that there are aliens anyway, and that they’re living in intolerable conditions because…oh never mind because, since it raises all sorts of questions about what the aforementioned ginormous spaceship is doing floating above Johannesburg.

Wikus gets sprayed with a peculiar substance which also serves to power a smaller flying craft that the aliens have down on the ground. Whatever it is, it’s not very economical, since it’s taken twenty years to fill a flask with it. And, err, it also serves to mix Wikus’s DNA with that of the aliens, so he slowly becomes a prawn. Meaning we can throw The Fly into the mix as one of District 9’s influences. That’s The Office, Kafka, and The Fly…just for starters.

Once Wikus finds himself sporting a prawny hand in place of the one he’s used to, the tone shifts again. This time to a buddy movie. Wikus and one of the prawns become allied in time-honoured fashion, and next thing you know it’s getting all Lethal Weapon as the two become action heroes to take down the multinational’s HQ and recover the canister of DNA mutating fuel.

The change of tone and pace is frankly bewildering at times, but if you can put the illogical aspects to one side — bear with me on this — you’ll find District 9 an enjoyable science fiction romp that seems to be all kinds of things without ever settling down into anything coherent. Frankly it’s a mess, but it’s a fun one, and I expect good things from Blomkamp in the future. Mind you, I’m not convinced that said future should involve him picking up the conveniently dangled promise of a sequel — I have a horrible idea he’ll want to infuse it with genres that were unaccountably overlooked first time round and include dance sequences and a serial killer.

As it is, there’s more than enough to keep your attention occupied. A bit of conspiracy thriller, a touch of comedy (even if it’s not deliberate — I seemed to be the only person laughing in the screening I attended), some macho action, a transformer robot, and some badboy Nigerians hoping to eat the hero in the belief that doing so will pass his mysterious powers onto their boss. You can’t fault District 9 for lack of invention, though maybe in the rush of enthusiasm that clearly went into creating this film some ideas really should have been dropped. But hey, with Peter Jackson shepherding the film into existence, a man never knowingly understated, perhaps it’s no surprise that District 9 seeks to be all things to all audiences.