For those sci-fi fans who grew up pre-internet and for whom listening to the 'War of the Worlds' album, buying Starburst or having 'Star Wars' on a treasured VHS tape were all big deals, one of the most memorable TV images may have been the scene in 'V' which showed the alien spacecraft hovering over the world's cities. That nostalgia trip kicks in once again watching 'District 9', but Neill Blomkamp's film will fare far better 25 years down the line - and gives you a lot more to think about.

In 1982, a huge alien ship arrives on earth - not above New York, Paris or London but Johannesburg. It seems that nothing has left the ship, and there is no contact made with people on the ground. Eventually the authorities decide to investigate.

On entering the ship they discover that its alien inhabitants are all close to death. They are taken to a special camp in Johannesburg, District 9, and receive food and medical treatment.

Fast-forward twentysomething years and the alien population of 'District 9' has swelled to nearly 2m and the people of Johannesburg want them all to go home. The aliens, nicknamed "prawns", are seen as lawless and dirty - stealing and destroying personal property and living in squalor. Charged with trying to keep them in line is the military giant Multinational United (MNU).

MNU's latest plan to ease the crisis is to move the aliens to a new camp much further away from Johannesburg and restrict their movements even further. In charge is Wikus van de Merwe (Copley), the son-in-law of an MNU boss and a man eager to impress anyone - superiors, subordinates, camera crews or aliens.

On the first day of the big move, Wikus enters District 9 determined to make a name for himself. By the end of the day he will have, but for very different reasons than he imagined.

One of the big hits of the summer in the US, 'District 9' has 'Lord of the Rings' director Peter Jackson behind hit (as producer) and is another treat for sci-fi fans after the much acclaimed 'Moon'. It looks great (you start to feel dirty and hot yourself), has excellent special effects and a message behind the mayhem - whereas 'V's was about fascism, 'District 9' is concerned with xenophobia and big business. Using documentary-style talking heads and a cast of unknowns, director and co-writer Blomkamp cranks up the feeling of real-life dread as the story unfolds. You suspect that he's not too fussed about happy endings. You're right.

Where Blomkamp disappoints is in the characters of Wikus and the aliens. Because of the way the story builds up, it takes some time to realise that Wikus is the actual 'hero' and the problem is that you never warm to him. Copley does a good job as the corporate stooge who realises he's part of something far bigger, but despite everything that happens to him the emotional connection isn't there.

As for the aliens, you're so suspicious of them from the outset that changing your opinion is a big ask, and even when you find out what their plan is, you're still not convinced they're on the right side. Maybe that's all part of Blomkamp's plan for the future, but you won't be looking at them like you did 'E.T.'.

If ticket sales are anything to go by, there'll be the chance to put these shortcomings right in the sequel. Until then, there is plenty to enjoy here. And just like 'V' made sure that some never saw mice in the same way again, 'District 9' will do the same with, eh, cat food. You have been warned.

Harry Guerin