Making a film about Jonah Lomu’s life was never going to thrill everyone. The big man’s widow, Nadene, took legal action in an unsuccessful attempt to block the project and declined to be involved. You can’t imagine Mike Catt being overly delighted either. Even 31 years later, the brutal footage of Lomu running straight over the top of England’s full-back in the 1995 World Cup semi-final in Cape Town almost merits an 18 certificate on its own.

Happily, the makers of Lomu went ahead regardless and have managed to shine a fresh light on the biggest rugby phenomenon in history. There was always way more to Jonah’s story than a huge pair of thighs and here it is, laid out in a manner that is thought-provoking, affecting and wincingly nostalgic. As the former All Blacks doctor John Mayhew puts it: “I’m disappointed he didn’t have the life he deserved to have. I wonder, even [with] the magnificent gifts he had, whether he was ever truly happy.”

That last, haunting line accompanies the viewer all the way home. The film, an artful blend of compelling archive footage, honest contemporary interviews and an evocative soundtrack featuring a range of traditional Tongan music, also puts this weekend’s crucial Test between the All Blacks and South Africa into perspective. When it comes to global recognition, how many of New Zealand’s current XV will merit a culturally important feature film 30 years from now? All of us who saw poor Catt being steamrollered at Newlands barely knew the half of it.

Even the All Blacks management at the time were unaware, for example, of the full extent of Lomu’s illness, which forced him to have a kidney transplant and foreshadowed his untimely death from a heart attack in 2015 at the age of 40. Mayhew, interviewed shortly before his own death in April last year, did not disclose the magnitude of Lomu’s health problems to the national head coach John Hart for a couple of years, the latter assuming the player must be lazy instead. “He was a rugby superstar playing in a body that had 70% capacity,” reflects Hart now. “I just wonder, if he had been at 100%. You’d never see another like him.”

In the background were a multitude of family and societal issues stemming from Lomu’s upbringing as the son of Tongan immigrants on the mean streets of South Auckland. As anyone who saw Once Were Warriors back in the day will testify, it was a seriously tough environment. The Irish film-maker Gavin Fitzgerald, whose previous work includes films about Conor McGregor and Liam Gallagher, and his New Zealand-based female co-director Vea Mafile’o believed that some complex cultural issues needed airing. “I never felt I was just telling a sports story,” says Fitzgerald. “Obviously, the rugby is a driving force of the narrative but, for me, the aim was always to get into the human side and tell something deeper that people could learn from.

“Everything I knew about Jonah, I figured out, was told very much through a western lens. His backstory was quite simplified. ‘Here’s a tough kid from the block who found rugby and it saved him. He’s angry at his dad and that’s what makes him good at rugby.’ But when you open up the Tongan in him, all these aspects get more nuanced.”

Jonah Lomu in full flight was a beautiful sight for the All Blacks but terrifying for the opposition. Photograph: Dean Treml/Photosport

Having trawled through hours of private family video footage and interviews, Fitzgerald is convinced Lomu’s upbringing was a significant source of tension in his life. “There was this clash of cultures … that he wasn’t sometimes Tongan enough for the Tongans. And then on the other side of the coin, he’s basically being told to act more like a palangi [white guy]. So I think it was tough to be Jonah and that was a central theme in the film.

“I think the older he got, the more that began to kind of weigh him down. His condition was obviously deteriorating and I think his life just got increasingly complicated. Fame is not everything it’s cut out to be. He was a God-gifted talent but he was given a curse as well.”

Mafile’o, who hails from two villages away from Lomu’s Tongan family roots, also wanted “to celebrate him properly” and dispel a little of the negativity that has latterly clouded his legacy. She says the film has proved a source of relief for the majority of Lomu’s family, who have been touched and strangely reassured by its release. “I saw members of his family at the weekend and it’s like a weight has been lifted off them. I think, from a cultural perspective, it’s released them from a lot of shame. I think even a lot of Tongans have been super-surprised at how Tongan he actually was. Thankfully the response has been really great. His mother and his brother are behind the film even though it is tough subject matter for them. It does show warts and all.”

There are also some lessons, reckons Fitzgerald, for New Zealand’s rugby authorities to absorb. “I think he could have been protected a lot better by the institutions, given how much he gave to the game. New Zealand Rugby finally has representation from that community at board level but that took an awful long time. It was a very white institution.” Mafile’o hopes the film will update perceptions further.

skip past newsletter promotion

Sign up to The Breakdown

The latest rugby union news and analysis, plus all the week’s action reviewed

“When you’re breaking glass ceilings someone has to fall, so to speak. Now there’s much more support around players and he was the beginning of it. I think people are just realising the full extent of the hardships he went through. That in itself has created also a sense of relief for the family. It’s almost like the truth has been revealed.”

Rewatching the cautionary tale of rugby’s man mountain being cruelly laid low by health and financial concerns there are also faint echoes of the Elvis Presley biopic released in 2022: a shimmering star with a gentle soul lured on to the jagged rocks of toxic celebrity by people who supposedly had his back.

Extravagant sporting talent, as everyone knows, doesn’t guarantee a happy ending. Jonah clearly struggled to resist a fast car but, then again, how many rugby players have ever experienced such a vertical ascent into the global consciousness? Go and watch Lomu to be reminded of a rugby player who singlehandedly changed the game. Come away wondering if, ultimately, all that God-given talent was too heavy a burden.

Lomu is in UK & Irish cinemas for one night only on Monday 7 September. Book tickets here: lomu-doc.com