Good grief. It must have been genuinely terrifying to be old, weary and conservative in the United States at the end of the 1960s. Sure, Nixon had just been elected, but he relied on a mass of older voters to propel him to the White House. Heaven help civilisation when the young properly took over.

The film studios were more puzzled than anyone by the rise of the counter-culture. The end of the decade saw more than a few delightfully deranged psychedelic productions green-lit by men who couldn’t tell the difference between The Monkees and The Velvet Underground.

It remains an amusing irony that – though Dennis Hopper's The Last Movie has a claim – the most extravagant manifestation of this phenomenon came from a 58-year-old Italian who had been directing since the second World War. MGM allegedly gave Michelangelo Antonioni, who had recently triumphed with Blow-Up, $7 million and allowed him the freest of reins.

Antonioni cast conspicuously untalented young people as a couple of students who, following various political engagements, head deep into the desert and discover themselves. There is a great deal of unnecessary plotting – amazingly five people, including Sam Shepard get script credits – but the film still comes across like a groovy free-form symphony aching for its closing epiphany.

When it arrives, man, it arrives. The main body now seems like a charming pastiche of faded values. But the literally explosive finale, scored to Pink Floyd's Careful with that Axe, Eugene, featuring consumer items blasted into the cobalt sky, still properly blows the mind. That is the phrase.

Nine years later, the young people helped elect Ronald Reagan.