As quixotic quests go, it’s a doozy: take 96 hours of raw footage filmed during one of the craziest and most tumultuous shoots in movie history and attempt to create a new version of the film described by Variety on release in 1979 as “a moral Holocaust”.

Step forward Thomas Negovan: the man who rescued Caligula. “There were definitely a lot of points in the last three years where I thought I was crazy,” he says. “I thought: ‘Is anyone going to care about this?’” But, in fact one of the most important entities in the industry, the Cannes film festival, cared very much, booking the new-and-possibly-improved version a premiere in its prestigious Cannes Classics strand, a section of the festival generally dedicated to celebrating the art of cinema at its finest.

“And so all of a sudden, I thought: ‘OK, all the therapy bills are worth it,’” says Negovan.

Screened for the first time on Wednesday, the 2023 version is billed as Caligula: The Ultimate Cut, and Negovan is keen to point out that, “The thing that’s bizarrely unique about it is it’s almost like the version that was released in 1979 is the deviant version. Ours is closer to what was originally intended. Even the word restoration … I don’t know what word works, but it isn’t a restoration. I don’t know what to call it.”

A quick recap for the uninitiated: involving more drama than every season of Love Island combined, the 1979 swords-and-sandals shockfest Caligula has long been infamous as one of cinema’s most disastrous productions, its very title a byword for what can happen when a creative project spins out of control. Starring Malcolm McDowell, Helen Mirren, John Gielgud and Peter O’Toole plus a busload of porn stars, the lurid epic about the life of the mad Roman emperor Caligula, was a noble attempt to create the most explicit prestige picture in the history of the moving image.

An anonymous crew member described it as “not a shoot, it’s the Fourth Reich. Caligula Uber Alles”. The finished film itself was hardly less chaotic. With finance put together by Penthouse founder Bob Guccione, a script by the leftwing intellectual Gore Vidal, and Tinto Brass, a cult Italian film-maker famed for his erotic movies, in the director’s chair, perhaps on paper the film had a certain sort of bold logic to it. Theoretically, these three brought to the table the unique combination of hedonism, intellect and wildcard creativity that the decadent, explicit, historical epic would need. What could possibly go wrong?

Everything, as it turned out, starting with a rocky development period during which Vidal fell out with everyone over changes to the script, and essentially disowned the film. Vidal would eventually call Caligula “easily one of the worst films ever made”, which is quite the review to get from its screenwriter. Of course, the film didn’t bear much resemblance to the screenplay Vidal wrote – as director Brass announced airily during production, “What we’re shooting right now is definitely not Gore Vidal’s script.” Producer Guccione also wasn’t impressed and wasn’t shy about saying so: “I’ve made the worst mistake in my life asking Tinto Brass to direct the film.”

For Negovan, the biggest tragedy of the original film is that the actors were left high and dry when they stepped on set and again when the film was assembled in a messy and contentious edit. Mirren, whose character gives birth in stirrups that leave nothing to the imagination (on stage in front of an audience), called the experience “an irresistible mix of art and genitals” akin to going into Dante’s Inferno.

Negovan believes that the original can fairly be described as “the clickbait edit” – in the sense that all the most extreme line-readings were favoured over subtler moments, which is fun in the moment, but doesn’t help the actors. His north star throughout the project was McDowell’s performance, which he felt was particularly undersold by the original cut. “Like, of course, Clockwork Orange is brilliant. But it’s not the same range that he has in Caligula. I feel like this is the best performance that Malcolm ever gave.”

There is something moving about Negovan’s quest to honour McDowell’s performance. There’s not much the recut can do about the script and iffy camerawork, which are all part of the charm. But Negovan has unearthed a much clearer sense of a character arc, from Caligula as wary young man genuflecting to the mad emperor Tiberius (Peter O’Toole, on wonderful form), to a joyful freshly minted tyrant, through to the increasing cruelty and disintegration of his reason as he is driven mad by power. Modern audiences, attuned to reality television and the way that an unfavourable edit can create an entirely different version of someone’s personality, are well-positioned to be more sensitive to the effect that the “clickbait” choices in the original edit has on the film as a whole.

Which is not to say that this isn’t the film fans know and love. Caligula’s strengths – the elaborate sets (particularly the head-chopping machine), the OTT costumes, the beautiful way that it is lit – are still present and correct. As are the multiple orgies, the infamous fisting scene, the copious nudity and the genuine shock of some of the violence. At the Cannes premiere of the new version, there were some walkouts following the scene where Caligula rapes both bride and bridegroom at a wedding; anyone expecting a purely silly cult movie may be surprised at how dark and upsetting some of it is – and always has been.

Caligula has an undeniable power to it, as an object as much as a film – it is a fiction feature and a documentary of a particular place, time and confluence of different creative energies, and this new version is a compelling testament to that.