Four businessmen (Jon Voight, Burt Reynolds, Ned Beatty and Ronny Cox) take a canoe trip down a Georgia river before it – and they – are dammed. 

Before temporarily scuppering his career with Zardoz, John Boorman shot this 1972 thriller on location without insurance, the actors doing all their own stunts – hence Reynolds’ self-referential line: “I don’t believe in insurance.” Just think, if anything had happened to Voight we might never have had Lara Croft: Tomb Raider – The Cradle of Life.

This makes Deliverance a feat of ’70s filmmaking, taking place almost entirely on dangerous rapids or a cliff face. The result is bracing and visceral, the action and emotion as real and deep as the river. Boorman and cinematographer Vilmos Zsigmond shoot the wilderness beautifully, initially conveying the expansive majesty of nature before closing in on wretched squalor as the camping trip becomes a fight for survival.

The same apocalyptic journey is reflected in the unique score, the iconic Duelling Banjos sequence offering the film’s final fun moment in the very first scene. As the rapids and violence intensify, the jaunty twanging gives way to eerie cicadas, and when the banjo music returns it sounds sarcastic.

Released the same lovely summer as Wes Craven’s The Last House on the Left, here’s another film about the middle classes stripped of their safety and reduced to primal instinct. “Machines are gonna fail and then the system’s gonna fail, and then? Survival,” says Reynolds’ character, enjoying himself a little too much – and wearing a wetsuit vest that’s scarier than anything in the movie.

Deliverance is a devastating deconstruction of machismo and the American myth long propagated by Westerns, that this land was built on the noble defeat of savages by explorers. For all its unpleasant hillbilly horror, the movie is surprisingly cerebral, and some of the most disturbing images are symbolic rather than graphic – a church being driven away to make way for the dam’s purging waters, its graves dug up, corpses refusing to stay buried.

It’s this balance of gruelling survival horror and haunting psychological depth that make Deliverance so dam frightening, particularly the ecological message – presumably lost on Voight – that when we destroy nature, we destroy ourselves. And always wear a life jacket.