Though not all work is naturally autobiographical, the extent to which the fictional world of The Sopranos steals small details from Chase’s real life is fascinating. The surname Melfi. The first name Livia. Small details, really. Though at times, one family tree looks built out of the branches of the other.

“I think it was autobiographical to some extent,” Gibney says. “But that’s the tricky thing about fiction. There’s autobiography in it and it suffuses the work. At the same time, you can’t treat it as pure autobiography because the characters in the dramas end up having their own valence and logic, and they grow into themselves.

“I think to some extent, [as he wrote it] the characters in The Sopranos stopped being purely David’s family and his own autobiographical experiences, and they began to be living, breathing people that were evolving in David’s imagination.”

In a traditional documentary environment – Gibney’s Going Clear: Scientology and the Prison of Belief, for example – there are competitive and complex forces creating a tension which in turn propels the narrative. In simple terms, documentaries work really well when everyone has a case to articulate.

The story of The Sopranos, however, is not an unhappy one. Indeed, for six years the creative team behind the series collaborated to build one of the most extraordinary television programs ever produced. Turning up to pat one another on the back cannot be that bad.

“I don’t look for tension,” Gibney says, laughing. “But when HBO originally came to me, I loved the series but wasn’t sure I wanted to spend my time doing a clip show. “But then I sat down with David and I found him to be such a fascinating character, and then I was intrigued both by the degree to which Sopranos had been a personal work, at least at the beginning.”

“You always look for complexities rather than tensions, I might use the word contradictions,” he says. “Sometimes you find contradictions, and you embrace them rather than running away from them. I was interested in the creative process.”

Gibney is, by his own admission, a fan. He could not say the same of his work on the Emmy-winning Mea Maxima Culpa: Silence in the House of God, or the Oscar-nominated Enron: The Smartest Guys in the Room.

And while sometimes meeting one’s idols is a challenge, Gibney says he came out of the experience unscathed. “It didn’t give me any pause because I knew I wanted to get inside it, so I knew I was going to have to go there,” he says.

“Long ago we did some work with Van Morrison, whose music I adore [but] the person is not somebody I have great deep affection for and that can be discomforting. How do you learn to love the music again, having had a bad experience with the person?”

The subjects of the documentary all talk candidly, but for many there are still unresolved tensions and lingering questions. Not every story was neatly tied up. Some actors, such as Drea de Matteo, are still haunted by the fate met by their on-screen characters. And for everyone – except perhaps Chase himself – the final episode is still being reprocessed.

“They were a group, but they were also a group of individuals who sometimes approached it very differently,” he says. “But I think that there was an insistence on emotional authenticity in the series that infected everybody and gave them both a sense of enthusiasm, but also dread, fear, happiness, it ran the gamut. It was deep for all of them.”

Which brings us to the most complex questions in The Sopranos′ story: that final episode. And in particular, that final scene. For those who have not seen it – warning: 17-year-old spoilers ahead – the final episode leaves the audience uncertain of Tony Soprano’s fate.

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In the scene, the Soprano family is eating at Holsten’s diner in Bloomfield, New Jersey, and the mood is set for what feels like an imminent assassination. Except it then fades to black and remains silent for 10 excruciating seconds.

Setting aside the fact that many people thought the TV signal had simply been lost, the decision was a creative choice by Chase, and the subject is tackled in the documentary. We will not go into any detail here, for fear of spoiling the analysis of the world’s most confusing spoiler.

“As a totality, I wasn’t focused so much on the very, very end, but it is true that from the beginning I thought I would spend and focus more time on the first episode and the last episode,” Gibney says. “It’s a bookend. Those are the two episodes that David directed, the only two.

“It became a much bigger cultural moment than just a director deciding how to end an episode,” Gibney adds. “And I was coming at it more from the blank piece of paper: what were you thinking about what you wanted to do? And that’s where I got some unexpected answers.”

Wise Guy: David Chase and The Sopranos screens on Foxtel and Binge from Sunday (September 8).

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