It’s suitably documented how Pavlov’s dog developed an innate response to repeated events, but did they stick around to see what happened when it got bored and sick of the sound of the bell? Was it ultimately able to fashion the "whatever" hand gesture with its paws?

I’m just wondering, as there have been some 60 years of celluloid alien invasions of Earth, responses to the threat of intergalactic occupation may peter out a bit. So I’m all a bit giddy, and fashioning large pointy foam fingers and celebratory bunting in honour of this smart and inventive film-making.

Turning the entire invasion angle on its head, District 9 finds a swarm of alien immigrants reluctantly pitching up in Johannesburg after their ship grinds to a halt. With the upper echelons of the society wiped out by a virus, only the poorer, less educated schmucks of the species remain, themselves weakened and malnourished.

Under global pressure, the South African government take the creatures in, housing them in a makeshift camp, which rapidly degenerates to a shanty town. With public hostility to the immigrants at a high, plans are made to relocate the aliens to a more remote area, segregated from an unwelcoming society. Wikus van de Merwe (Sharlto Copley), a jovial bureaucratic idiot, is instructed by a local authority to oversee the move, with the aliens’ rights seen as an obstruction that can be overlooked if necessary.

After accidentally getting infected during a search of an alien’s shack, Wikus finds himself having more in common with the aliens than he'd like, which in turn throws him unwittingly and painfully involved into the government's darker intentions towards their intergalactic guests.

From Blair Witch to Paranormal Activity via Cloverfield, the fake documentary genre has shown that rather than being a gimmick, it’s a format that will allow your film to flourish if you have a solid and imaginative premise. Smoothly working between retrospective interviews and the events of Wikus’ attempts at relocation, it cannily binds the events with the ensuing cover-up, as the shocking tactics of the authorities are laid bare.

Setting it in South Africa is a massive part of the story. Clearly, the underlying analogy with apartheid is unmissable, but it serves to add a further level of tension, rather than form the basis of a political tirade. This means that as the film swerves into a more conventional action film narrative, it doesn’t feel like the social critique is binned, it was only ever a framework for the events.

The location and kwaito soundtrack, both abundantly provincial and genuinely turbulent, also lend it a world cinema edge, making it a kind of City Of God for sci-fi heads.