Image copyright El Grafico Image caption Diego Maradona had England in a spin at the 1986 World Cup by scoring both goals in Argentina's 2-1 victory; one with his famous left foot and other with his infamous left 'hand of God'

Like many of us, Asif Kapadia seems to prefer his heroes when they're fundamentally flawed.

From the Bafta-winning Senna; the tale of the life and tragic death of Brazilian F1 racer Ayrton Senna, to the Oscar-winning Amy; which chronicled the rise and similarly sad fall of the singer Amy Winehouse, the British director has specialised in telling stories surrounding a complicated genius.

Few are more fitting of that description than the Argentine football star Diego Armando Maradona.

Not for the first time the troubled figure, who tormented England at the 1986 World Cup, finds himself the subject of a new documentary - which premiered at the Cannes Film Festival on Sunday night.

Kapadia's version focuses largely on his explosive spell with the Italian club Napoli, with its glorious on-field highs and his painful cocaine-induced lows.

Image copyright AFP Image caption Maradona is now the manager of Mexican side Dorados

Ahead of its world debut, the film's producer James Gay-Rees tells the BBC about the unforgettable time his director friend got up close and perhaps a little too personal with the film's title star.

"Asif did the interviews," he explains down the phone, en route to the festival.

"He was in his [Maradona's] house in Dubai interviewing for the first time and Diego was watching the football in the background, which is a challenge.

"So to angle the camera on Diego he ends up kneeling on the ground.

"Maradona was in his shorts and his left leg was stretched out and Asif thought 'that was the foot that was blessed by God!'

"He couldn't help it, he said he had an out of body moment and reached out and touched his leg.

"Maradona was like 'what are you doing?!'"

Image copyright Getty Images Image caption James Gay-Rees (l) and Asif Kapadia with their Oscars awarded for Amy in 2016

The producer-director duo, along with co-producer Paul Martin, could not resist "the opportunity to get inside Diego's head" either, says Gay-Rees, "and see what made him tick and to try and make sense of it".

Serbian director Emir Kusturica attempted the same feat in 2008 with his documentary which followed Maradona for two years and was similarly shown at Cannes.

The various off-screen narrators of Kapadia's effort, including the man himself, talk of there being two very different characters at play during the story of his life; First, 'Diego'; the football-mad boy from Buenos Aries, and then there's 'Maradona'.

Whether or not making sense of either of them is humanly possible on film or elsewhere is another matter altogether.

"If you want to understand him now you have to understand his rich turbulent period in Naples," adds Gay-Rees.

"It was a wonderful opportunity. I'm not sure we entirely got to the bottom of Diego, because I don't think you can."

'Safeguard against getting kidnapped'

The 58-year-old star, who is now the manager of Mexican side Dorados, missed the film's premiere on the French Riviera, due to "a shoulder injury requiring medical attention," his publicist confirmed on the day.

The idea for the feature, which was screened out of competition at Cannes alongside Dexter Fletcher's Elton John biopic Rocketman, came about while Gay-Rees and Kapadia were still working on their Amy Winehouse film.

They were alerted about the existence of some unseen footage belonging to two cameramen in Naples.

The footage was apparently commissioned at the time by Maradona himself, in order to help him hide in plain sight.

"He shot the footage as a safeguard against getting kidnapped," reveals the producer.

"He wanted a record of his whereabouts.

"The town was run by The Camorra [mafia] and they partially financed his move [from FC Barcelona] and he ended up closely aligned with them.

"When Amy was finished Paul and I jumped on a plane to Italy and met them.

"It was great, unfiltered material. You need that hidden stuff that people haven't seen."

They were also granted court subpoenas to release revealing calls recorded by the Italian police who had been tapping Maradona's phone.

"We were pleasantly surprised when we were granted that material," laughs Gay-Rees.

Image copyright El Grafico Image caption The new film shows footage of a young Maradona with his mother Dalma and father, also named Diego

'Force of nature'

As for working with the man/the myth himself - leg touching incident aside - there was a bit of mutual respect going on, it seems.

"He was great," beams Gay-Rees.

"Diego is Diego, I can't pretend I know him very well - he's a force of nature.

"He liked our previous films as he and Senna were in Italy at the same time and both doing great things.

"I don't think there's a massive analysis about the decisions he makes and there were no editorial handbrakes put on us at all - he's not that bothered."

Now the film-makers, who between them have also worked with the likes of Cristiano Ronaldo, Oasis and Banksy, have another controversial hero in their sites.

"The one we'd like to do is Mike Tyson, as I don't think the definitive Tyson film has been done yet.

"Even though Tyson is scary and Diego is crazy they are likeable and you have to be slightly romantic and fall in love with the characters if you're going to take on this challenge."

Diego Maradona is out in UK cinemas on 14 June