"I didn't want this to be a film about abuse" – how a new Whitney Houston biopic handled a shocking revelation

Still, most were as nothing compared to trying to pin down his latest subject, one of the titanic figures of 80s pop, a singer whose squalid decline and death were in sharp contrast to her glorious musical talents. When Macdonald agreed to make an authorised documentary about Whitney Houston, he admits he didn’t appreciate that a true portrait of such a big star would prove so slippery.

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A killer soundtrack of I Wanna Dance with Somebody and I Will Always Love You does not make an insightful doc. But, rather than providing answers, full access to friends and family agreed by the Houston estate simply raised more questions. “It was an odd film to make because it was so hard to get at the substance. Whitney is an elusive individual – it’s very, very hard to pin her down,” Macdonald says with the weary authority of a man who spent 18 months planning some 70 interviews and poring over hundreds of hours of archive footage.

“She doesn’t really tell you who she was. She was very rarely honest in interviews.”

It’s to Macdonald’s credit, then, that Whitney (in cinemas from Friday 6 July) is brilliant... entertaining, compelling and, ultimately, heartbreaking, it’s a striking addition to the booming rockumentary canon, a worthy bedfellow to Asif Kapadia’s Oscar-winning Amy.

Macdonald previously wrestled the many lives and loves – and children – of reggae legend Bob Marley into a single film. But this has the bonus of a bomb-shell cinematic revelation at its core. Want to understand how one of the brightest stars of the MTV era ended up overdosing and drowning in a hotel bathtub in 2012 aged only 48? At last we might have the answers.

Macdonald achieved this by digging deep. He investigated the backstory of her father-turned- manager John Houston, an embittered Second World War veteran whose determination to beat American racism drove his financial ambitions, which later evolved into an ugly financial battle with his daughter. He found out that her mother had an affair with their preacher, “so the church is blown apart for Whitney”. The film-maker researched the New Jersey milieu in which the three Houston kids were raised, a street-tough existence scarred by the early 1980s crack and cocaine epidemic.

He interviewed Whitney’s inner circle – brothers Gary and Michael, her PA Mary Jones, her acting agent Nicole David – multiple times. This doggedness exploded the terrible secret at the heart of Houston’s dreadful demise: she was sexually abused in childhood by her cousin Dee Dee Warwick, singer Dionne Warwick’s younger sister.

Having uncovered these traumatic details from Houston’s past, Macdonald realised he now had a reason for her elusiveness. And a context for her drug use. But now that he had his headline grabbing scoop, how did he avoid tabloid sensationalism?

“I certainly didn’t want the film to feel exploitative,” Macdonald nods over a glass of wine in a pub around the corner from his north London house. “I always felt it was a mission of understanding.

“I wanted the first half to be basically a good time – take you back into the 80s, listen to her greatest hits, that voice, which is what it’s all about. Then when the revelation comes and you loop back, you hopefully see the first two-thirds of the film in a different light. I didn’t want people to think of this as a film about abuse.”

Macdonald was beaten to the screen by a rival project from documentarian Nick Broomfield, whose unauthorised Whitney: Can I Be Me is, Macdonald thinks, undone by lack of access, and by what he sees as a core fallacy: that the key to the mystery of Houston is a forbidden same-sex love affair with her friend and former assistant Robyn Crawford.

“I respect Nick, I like Nick as a person, and I’m sure there are good things about the film,” he says of a doc he admits he hasn’t seen. “But beyond everything else, documentary should be truthful. If you’re basically making up a story about what you think from the outside is the truth, it’s not in my mind a great way to make a film.” Still, there is one Broomfield-esque trick in Macdonald’s film. Towards the end of this meticulously detailed, deep-dive portrait of the artist, we occasionally hear the director’s soft Glaswegian burr interrogating his sometimes squirrelly contributors.

“Yeah, I hate the sound of my own voice,” he smiles, squirming even now. “But I did that very late on, trying to structure the film. I felt there was so much mystery, and so much of a sense of people not telling the truth, that I wanted the audience to feel like I was a bit of an investigator.”

Those sleuthing documentarian skills will serve him well on one of his upcoming projects. Macdonald is partnering with Channel 4 on a four-part drama about the 1988 Lockerbie bombing. He’s also hooking up with Benedict Cumberbatch’s SunnyMarch production company to adapt Guantánamo Diary by Mohamedou Ould Slahi. “The most tortured man in Guantánamo, who was found to be innocent. He’s an amazing character. He has a sense of humour about being locked up for 15 years.”

It’s all a long way from the films of Kevin Macdonald’s illustrious grandfather. In tandem with Michael Powell, Emeric Pressburger made some of the greatest British films of the 1940s and 50s, including The Life and Death of Colonel Blimp, A Matter of Life and Death and The Red Shoes.

“I have him to thank for my passion about cinema, but not in the obvious way,” he says, pointing out that, after graduating with an English degree from Oxford in 1988, the only “job” he could get was writing a book and making a “terrible” documentary about Pressburger. It set him on his film-making path. “What I’m interested in doing is largely truth-based. Whereas he and Powell were interested in the opposite – looking at reality through a veil of fantasy and imagination.”

Still, there are few contemporary film-makers who can handle the truth as imaginatively as Kevin Macdonald.