It seems that there are people on Earth - even in Britain! - who still haven't seen Brazil. A while back I actually met some Britons in their early twenties who had never heard of it. This troubles me greatly.

Terry Gilliam's 1985 dystopian classic is beautifully realised, often hilarious and utterly horrifying, not least because it has turned out to be so prophetic.

Fundamentally - and very coherently - this is a film about systems breaking down: A dead fly drops into a printer, causing a misprint which leads to a man's mistaken death by torture; heating systems break down, and cannot be repaired because the Central Repairs support system is overstretched; the ubiquitous, massively complex systems of machines, presumably designed to make life easier, invariably go wrong when one or another link breaks down.

It is also a film about systems breaking down humanity. With everyone having their own tightly defined role in the overarching bureaucratic systems that control everything, nobody has to take personal responsibility for anything else; mistakes are almost always somebody else's problem, and nobody really feels they have the power to change anything. Throughout the film it's therefore difficult to pin much of the blame for any of the things that go wrong on any particular person. Even the head torturer (Michael Palin) gives the impression that he's only getting on with his job, the same as anyone.

Almost all of the action of the film is driven by people struggling against these systems of control, whether by fighting back or (more usually) working around them. Our main protagonist, the affable dreamer Sam Lowry (Jonathan Pryce), is bent on using his access to the Ministry of Information to find out more about the woman he thinks he loves, Jill Layton (Kim Greist), a quest which is complicated by the fact that she is considered an enemy of the state thanks to her efforts to find out what happened to her neighbour, the unfortunate victim of a clerical error. The closest thing we have to a hero in this story is Harry Tuttle, a renegade heating engineer played with much panache and very little restraint by Robert De Niro.

This was Gilliam's third non-Python feature, after Jabberwocky and Time Bandits, and it maintains many of the comedy tropes of his earlier work. Although it is hugely over the top, with much of the melodrama played for laughs, the comedy aspects largely just add to the unease of it. This is a world gone utterly mad, but it nevertheless seems disquietingly plausible: The built-in unreality means it makes that much more sense when we find a cheerfully absorbed secretary typing up transcripts of hideous torture sounds, or we witness negotiations for a payment plan to cover the cost of someone's own 'interrogation'. How far are we from that sort of world right now? How much closer than we were when Brazil was made? For my money this is more disturbing than any film I've seen marketed as a horror.

The story is interspersed with dream sequences, and next to the profound oddness of the reality they interrupt, it ends up increasingly unclear where one ends and the other begins. The dream sequences themselves are gorgeous and unsettling, even if their allegorical relation to the rest of the film veers between brutally unsubtle and rather obscure. Our protagonist flies on Icarus-like wings through fields of billowing clouds, over grim, haunted concrete landscapes, towards his dream woman. As the world throws maddening obstacles in his way, from eruptions of tower blocks to a huge robotic samurai, our dream-Sam valiantly fights his way through them, only to be thwarted again and again. It is in these dream sequences that it becomes most obvious this is a Gilliam film - everything about them could have come straight out of one of his animated Monty Python sequences, rendered with real actors, puppets and the best special effects that 1985 had to offer.

The aesthetic of the real-world part of the film is equally striking. Costumes and sets place it some time around the 1930s, with technology perhaps extrapolated from that period in subtly different directions from the ones it actually took. Computer screens are tiny, unsheathed cathode ray tubes with great Fresnel lenses hung in front of them for magnification. Documents are shot from place to place using tubes. Indeed tubes of various sorts are a major motif of the film, prominent ducts snaking across the oppressive monolithic architecture in almost every shot, a visual metaphor for the tangled, high-pressure systems everyone is pushed through.

Brazil is obviously a satire, but it also belongs to the tradition of visionary dystopian science fiction. Gilliam's targets are trends which he must have been dismayed to see not just continued but greatly strengthened in the decades since. His conception of humanity's descent into inhumanity has so far proven much closer to the bone than such obvious inspirations as George Orwell's Nineteen Eighty-Four and Fritz Lang's Metropolis, and right now there is little sign of us making any major collective effort to get off this course.