When we first encounter the subject of fashion documentary McQueen, he isn’t what you might expect.

“I saw this unprepossessing, very shabby, very unattractive boy with a bundle of clothes over his arms,” says Bobby Hillson, founder of the St Martins MA fashion course that Alexander McQueen took, and one of his key mentors. Another says: “He’s got nothing. No money, no studio, no wherewithal, nothing behind him. And yet … ”

The film, by directors Ian Bonhôte and Peter Ettedgui, takes that “and yet” and unravels it.

McQueen’s monumental success can only be attributed to his extraordinary work. He found inspiration in the dark corners of his soul and put the results on the catwalk: clothes based on violence, sex, and – particularly towards the end – death. His work was attention grabbing, uncompromising and often brilliant. But there’s more to him than that.

“What we didn’t want was a bunch of fashion A-listers talking about how marvellous Alexander McQueen was,” says Ettedgui on the phone from London.

He had his work cut out. Plenty has already been said about the prodigious designer who worked with Givenchy and Gucci, dressed Bowie and Bjork, and tragically took his own life at 40. And Ettedgui is open about the McQueen family’s initial “ill feeling” towards his and Bonhôte’s attempts to make the film (though in the end they got unprecedented access to McQueen’s archives).

Ettedgui says he doesn’t even know much about the fashion world.

“Ian is the fashion one,” he says. “He’s always immaculately dressed. I’m usually in a pair of jeans and a work shirt.”

As a young man in London in the ’90s, Ettedgui says McQueen’s name was hard to avoid. It was the very apex of popular culture, like the Young British Artists movement and Britpop.

“Every time he did a show, the tabloids were scandalised,” Ettedgui recalls. Soon, McQueen was in the same vein as artists like Damien Hirst and Tracey Emin.

“This film is me coming home to a world I grew up alongside, but knew nothing about,” Ettedgui says.

His father, a fabric retailer who frequently worked with big-name designers, taught Ettedgui that behind the shock and glamour McQueen was a master tailor who learned his craft on Savile Row in central London, known for its bespoke tailoring for men.

“I remember being intrigued,” Ettedgui says. “On one hand he’d mastered the tradition, and he was turning everything upside down. He was a bit of a Picasso figure. But you have the human being as well, and that’s a fascinating story.”

McQueen grew up working class in Lewisham, south London, about as far from the fashion world as you can get. He arrived a complete outsider, but in a few short years he was royalty.

In the film, a slew of posh voices express astonishment at McQueen’s raw talent and absolute lack of regard for everything that stood between him and success. He looked like a normal bloke down the pub. He bought fabric with his dole money, and charmed people into working long hours for free.

Approaching friends and family about his intent to make the film, Ettedgui says he encountered some hostility. It’s understandable. McQueen is prime tabloid fodder, the quintessential tortured artist, a misunderstood outsider plagued with mental illness, and gone before his time.

“We wanted to get as powerful a sense as possible that [McQueen] was driving the film,” says Ettedgui. “This is him in his own words.”

Those words are literal, through previously unseen home movies and audio tapes, and metaphorical, through every design, every stitch, and every highly allegorical catwalk installation documented. The film makes the most of McQueen’s visual flair. His shows transcended the catwalk. A model spins on a pedestal while robots spray paint her white dress. A curtain falls to reveal a glass cage with an obese woman wearing a kind of gas mask, flanked by moths.

The darker aspects of his personal life are there, but the focus is on how he channelled it into his work. Everything else – his suicide, drug abuse, his health – is gossip.

“Certain things became, if not excluded, less important,” says Ettedgui. “I feel like I’ve seen that story before. We want it to register, to hit home. But if you talk about that stuff too much, people won’t be thinking about McQueen, they’ll be thinking about those aspects of his life.”

Ettedgui treads particularly careful around the facts of McQueen’s background as a victim of child abuse.

“His family talked about it changing his view of the world, giving him an outlook that that no person should have at that age,” says Ettedgui. “And you can see that in his creativity. There’s that sense of damage and decay in his work, yet he wanted to empower people.”

“What McQueen always said was if you want to know me, look at my work. That’s the manifesto for this film.”

McQueen is in cinemas now.

Watch the trailer here.