Visit Napoli today and it is impossible to escape the grip Diego Maradona still holds over the city. It is more than 30 years since he led them to their first Serie A title in 1987 and into the European Cup, but his image still adorns buildings across the city. One giant mural, in the San Giovanni a Teduccio district, is called Dios Umano: Human God.

Celebrations lasted two months, such was the passion of fans upon clinching that first title. Twice Napoli won the Scudetto during Maradona’s time at the club, as well as the UEFA Cup. This unprecedented period in the team’s history comes into sharp focus in director Asif Kapadia’s latest film: Diego Maradona. Thrilling, shocking, profoundly moving, the documentary uses previously unseen footage to chart the extraordinary highs and lows of Maradona’s spell in the city. A roller-coaster story to rival anything dreamed up in Hollywood, it gives unique insights into how an insecure kid called Diego achieved almost god-like status in Naples – only to see that adulation dramatically unravel. Kapadia’s previous documentaries on Formula 1 world champion Ayrton Senna and singer Amy Winehouse won him an Oscar and a clutch of BAFTAs, and his latest study of a complex genius has already garnered praise and positive reviews. A football devotee and Liverpool fan from an early age, here Kapadia discusses the result of his three-year journey into the life of Diego Maradona.

Was this your passion project?

I love football, I watch football, I play football. Apart from film-making, and before film-making, and before relationships or anything, there was football. There was always football. That’s what we grew up in my house watching and loving. I’m one of those Liverpool fans from the ’70s who has stuck with them. You’ve got to. Even though I’m north London and my family were mainly Arsenal.

You have done documentaries about Ayrton Senna and Amy Winehouse but, as a football fan, was there added pressure doing this one?

I do think it’s different. This is a character that I have grown up with. This is a guy that I have been aware of. I remember Diego in ’82. I can remember ’86, watching the [World Cup quarter-final] against England – the tournament when he came to the fore. This film, I guess, was about trying to reveal who Maradona was as a club player. And what football was like then – old football. That era of our film is where the Champions League begins. It’s very different. It’s football from another planet, almost, when you look at the tackles that used to go on.

You started by making a film about his whole life and then narrowed it down to Naples. Why was that?

Diego’s life is, visually, like a series of circles. He goes somewhere, there’s a lot of hope, everyone loves him, he does something fantastic. Then he’ll get into an argument, he’ll pick a fight, something will go wrong; it ends badly, he leaves, he goes to the next team. It’s the same story repeated, repeated, repeated. But the biggest story was Naples. At that time he was the best footballer in the world; no one touched him. He won the World Cup – and he won the championship with a team that had never won before and has never won since.

Maradona’s first visit to the Stadio San Paolo after signing from Barcelona looked like something out of a movie, even before you got your hands on it.

I think he was the first one to have that kind of event at his arrival at a new team. There were 80,000 people there to welcome him. That was just genuine passion from the fans at having an incredible star player. Now, pretty much every player, that’s what they are trying to copy. It’s the norm now but it wasn’t the norm then. And you have got to remember that Napoli, the year before he arrived, they nearly got relegated. They only saved themselves in the last match of the season. That’s kind of crazy. Players would just not do that now. The best players, at the very, very top, they kind of want to be guaranteed to win. They want to be surrounded by superstars. They need to be at the richest clubs. Maradona went to the poorest club and within three years won the toughest championship there has probably ever been.

‍In so much of the film, he seemed vulnerable. It’s a side to him that’s rarely been seen.

You know, when you think of Diego Maradona, particularly latter-day Maradona, you don’t think of someone who is quite lonely, or lost or vulnerable. You think of a macho guy who creates chaos and says controversial things. But actually, what I find interesting about this form of storytelling is that I’m looking at a young Diego arriving in Naples. I’m looking at him going: “I can see a child.” So he is a vulnerable kid. He is lonely, he is afraid, he looks scared when he is surrounded by people and crowds. You can see on his face when he’s unhappy, when he’s happy. That’s what I like about the film: we were able to show simple raw emotions. I don’t have to tell you how he is feeling; you can see it in his eyes. His eyes never lie. And it was a really key thing with Senna and Amy too. These three brilliant people, really amazing characters, but with all of them you can see the weight and the pressure on their shoulders, how their face changes, how their body shape changes as the pressure builds up upon them. And their release and way to express themselves is to do the thing they love. Diego, when he’s on a pitch, is in control. Everything’s cool, he knows what he’s doing. It’s everything off the pitch that is difficult to run and manage.