No production has been as troubled as the 1979 war epic. As behind-the-scenes documentary Hearts of Darkness is re-released, its director, and two of those who were on set, reveal all.

"The way we made it was very much like the way the Americans were in Vietnam," explained Francis Ford Coppola, after the Cannes Film Festival screening of Apocalypse Now in 1979. "We were in the jungle. There were too many of us. We had access to too much money, too much equipment, and, little by little, we went insane."

While the troubled production of Coppola's epic, brutal, psychedelic war film had been well documented in the press while it was being made – from finance issues to actors being re-cast, and health problems to extreme weather – it would not be until 1991 that the true extent of the chaos would become clear via Hearts of Darkness: A Filmmaker's Apocalypse.

The documentary was assembled from extensive footage that Coppola's wife Eleanor shot while on set, depicting a film production that while breathtaking in scope, ambition and vision, was equally messy, drug-addled, and riddled with seemingly insurmountable setbacks. Fax Bahr and the late George Hickenlooper were the two young directors tasked with combing through reel after reel to piece together the madness and tell the gripping story of the film's making. Now that film, having undergone a 4K restoration, is back in US and UK cinemas from this weekend.

Bahr still recalls the first day he saw Coppola's footage, which had been sitting, largely untouched, for over a decade. "Some of the reports had been, 'Oh, there's a lot of out-of-focus stuff,'" he tells the BBC. "But the reels we looked at were extraordinary. Just beautiful footage. Clearly, she had been copiously recording everything that was happening. It was absolute gold."

Apocalypse Now, loosely based on the 1899 novella Heart of Darkness by Joseph Conrad, is considered one of the greatest works in cinematic history. However, it nearly fell apart at various stages. With filming starting in the Philippines in March 1976, it was initially set to be a five-month shoot – but in the end would last over a year. Coppola fired his leading man, Harvey Keitel, a few weeks in, and replaced him with Martin Sheen, who then suffered a near-fatal heart attack on location. Expensive sets were totally destroyed by a typhoon, and some actors were infected with hookworm parasites, while others leaned into heavy partying and drug-taking on set.

Then Marlon Brando, who was playing the AWOL Colonel Kurtz, showed up on set heavily overweight and completely unprepared, which forced Coppola to re-write and shoot the ending of the film to suit him. As time went on, the film was so drastically over budget that Coppola took on the role of financing it himself, which would have ruined him had it not made its money back. According to Eleanor Coppola's book, Notes, even after the shoot had wrapped, during post-production, Coppola only gave himself a 20% likelihood that he could pull out a credible film from the wreckage.

The documentary paints a picture of a production that sets out to recreate the Vietnam war and, in many ways, ends up mirroring many of the same patterns of behaviour that took place among soldiers. One person suitably placed to make such a comparison is Chas Gerretsen, the Dutch war photographer and photojournalist who was brought onto the set for six months (the results were collected in the 2021 book Apocalypse Now: The Lost Photo Archive.) "Vietnam was insane, Apocalypse Now only slightly less so," Gerretsen tells the BBC.

The harsh conditions were totally alien to most people there. "The crew complained a lot about the heat, humidity, hotel rooms, bugs, mosquitoes," he says. "The mud – sometimes........

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