Lou Reed is the man in Cannes Velvet Underground film

Or so claims Todd Haynes, who has become one of the great chroniclers of rock n roll lore, in his new documentary about The Velvet Underground at the Cannes film festival.

Haynes has tackled difficult artists before, with an Oscar-nominated semi-fictional film about Bob Dylan ("I'm Not There") and a movie based on David Bowie ("Velvet Goldmine").

Now he turns to Lou Reed and his quintessential arty New York band, once managed by Andy Warhol, that helped revolutionise not just rock, but the way we look at gender and sexuality.

Haynes makes no bones about how hard it was to be around Reed, and how the Long Island suburbanite who was still living with his parents throughout the period stuck the knife in the back of his closest collaborator, the brilliant Welsh composer John Cale.

"These white guys were dealing with their demons and their anger and their self-destructiveness [in their music] and that's really true of Lou Reed," Haynes told AFP.

"It was really important to be honest about how challenging he could be," he added.

"You appreciate the artist but you recognise that their vulnerabilities and insecurities made them very difficult people to work with."

- Power dynamic -

There is no shortage of drugs and sex with the Velvets, particularly when it comes to the mercurial pan-sexual frontman.

But Haynes said, the film was "not a sex, drugs and rock 'n' roll gossip movie", even if he admitted that "someone could make a super-fun and interesting film like that about The Velvet Underground."

Instead Haynes wanted to show how the accidental coming together of "these five very different people" under the benevolent gaze of Warhol and his multimedia Factory "superstars" created "an absolutely unique moment in music history and in New York life."

For him, the Velvets opened the way for Bowie and glam rock and its antithesis punk as well as New Wave that drew from the same art school well.

"It inverted the power dynamic," Haynes insisted, a gender bending "which continues into Bowie and Iggy Pop. It was Bowie who introduced the world to The Velvet Underground" by playing their songs on Ziggy Stardust.

Reed's uneasy ghost he died of cancer in 2013 haunts the film, his disembodied voice accompanying Haynes' deep dive into avant garde 1960s New York thanks to his unlimited access to the Warhol archive.

In one unforgettable scene, Reed in mascara and sparkly blue nail-polish appears at the feet of a sceptral Warhol, chilled, reflective and a lot more compassionate that most remember him.

- 'Exposed and volatile' -

Reed's own sexual elasticity and the atmosphere of "permissiveness and the performativity of a different kind of masculinity" in Warhol's Factory helped make the Velvet's pioneers in playing with gender.

Haynes said Reed put "his neuroses and conflicts into his work in a way it was hard to find parallels to at the time. We are in period where amazing art and music was being made... yet there was nobody like Lou Reed and the Velvet Underground."

Cale and Reed later reconciled but Haynes argues that it was inevitable that their relationship would explode.

"They were both exposed and opening up to each other at the most volatile and unique time in their young lives. They were doing drugs together that separated them from the rest of the world.