Leaving Neverland has been seen by his many wild-eyed defenders as a “j’accuse” aimed at the legacy of Michael Jackson. It is not. It is a detailed, four-hour study of the psychology of child sexual abuse, told through two ordinary families who were groomed for 20 years by a paedophile masquerading as a trusted friend. It’s a mask that is often used by predators, whether a priest, a teacher, an uncle. This time the man behind the mask just happened to be Michael Jackson.

I had only a foggy idea about all this before starting work on the film. The complex, counter-intuitive and repugnant truths of child sexual abuse that Wade Robson, James Safechuck and their families have courageously unravelled on camera came as a shock to me.

In particular, the repellent but undeniable fact that a powerful attachment often forms between the predator and the child, who experiences the adult’s sexual advances not as abuse, but quite the opposite: as love. Equally disturbing to any parent is the child’s subsequent urge to shelter the abuser from parents or police. This misplaced loyalty often persists into adulthood, even though the adult knows by now that child sexual abuse is a crime. “I felt anointed,” as Wade puts it.

And then there’s the fear of consequences. “Michael told me we’d go to jail for the rest of our lives,” said Wade, describing a conversation that he had at Neverland when he was seven, but was repeated many times. The combined weight of love, shame and fear can lead to a lifetime of silence. The psychological strain of keeping the secret corrodes the soul, resulting in depression, feelings of worthlessness, substance abuse, suicidal thoughts. And the victim doesn’t connect these symptoms with the childhood sexual relationship. I am no psychotherapist but this all started to make a dreadful kind of sense to me. As James observed poignantly in a recent interview: “Your whole childhood is a lie.”

Facebook Twitter Pinterest Michael Jackson fans protest against the film. Photograph: Dingena Mol/EPA

And here is the saddest truth of all. We trust our children to warn us of any unwelcome physical contact by an adult. But what if – sickening though it sounds – they do enjoy it, and do feel special? Oprah Winfrey, herself a survivor of child sexual abuse, goes so far as to say that child sexual abuse is a misnomer; it should be called “child sexual seduction”. When Wade tells his mother that Jackson molested him, she turns to him: “How could you not have told me?” Wade chokes up as he describes this. “That’s a really complicated question,” is all he can manage to say.

Wade was in love with Jackson and cherished that relationship even more than the bond with his mother. That situation persisted for years. It wasn’t until after he became the father of a little boy that Wade “woke” and began to look for a way out of the accursed mental Neverland he’d entered 22 years earlier.

Everything about child sexual abuse is complicated, but that’s where the documentary form comes into its own. I’ve always believed that less is more and shorter is better, but what I realised – as the talented editor Jules Cornell and I put together the story over many months – was that this anatomy of two families’ ordeals demanded a far bigger canvas than any other story I’d tackled in my years of presenting complex stories of trauma through intimate personal testimony. This one takes four hours to tell and, until you’ve watched all of it, you’re in the dark about whether to believe James and Wade or not. Few who have watched it without prejudice are left in any doubt by the end.

By contrast, the counter-narrative from the Jackson camp has been aggressively reductive. “It’s all about the money,” they intone every time a new accuser emerges. This time though, there’s a second cudgel their legal and propaganda machine is using to beat the children that Jackson raped.

Wade was the first defence witness in the 2004/5 criminal trial of Michael Jackson. His testimony helped to acquit the King of Pop of molesting Gavin Arvizo, a child cancer survivor. Wade states in my film that he had perjured himself because he could not bear to see Jackson, the man he loved, go to jail. Telling the truth was out of the question. He had never told a soul, not even his mother. So the Jackson camp now call him an admitted liar. This argument falls apart when you apply even the merest dusting of common sense. Was he lying then? Or is he lying now? You can’t have it both ways.

The evidence of perjury of course comes from Wade himself. Part two of the documentary leads all but the most hard-bitten fan to an understanding of why he lied then, and is telling the truth now.

Play Video 2:55 What we know about Michael Jackson's history of sexual abuse allegations – video

The charge that James and Wade are in it for money is equally flimsy. In 2013, Wade (joined later by James in a separate, but similar case) launched a lawsuit against Jackson’s estate, claiming that Jackson’s business associates knew he was molesting little boys but turned a blind eye. Their cases were dismissed on technical grounds, but the judge made no ruling on the validity of the abuse claims. The cases have both gone to appeal.

So where will this “gold” come from? The answer is that Wade and James would have to win it in a hotly contested court battle. A jury would have to weigh up evidence – of which there is plenty – and decide that their claims were valid. And damages would then be awarded against the Jackson estate. Some people would call that justice. The most extraordinary thing in all this is that no one denies that Jackson took little boys to his bed, night after night, for many, many years. What did his family and business associates think he was doing with these little boys behind a locked door? Did they believe he was actually a child in the body of a man and therefore somehow needed to sleep with little boys? That makes no sense if you think about it for more than a second.

Why has it taken 30 years for Jackson to be unmasked? Here in the UK we were all asking the same question after Jimmy Savile.

The answer has something to do of course with the dazzling glare of celebrity and our instinctive deference to talent and wealth. But it also has a lot to do with collective ignorance. Joe Public – that includes me before making this film – has no idea what grooming by a predatory paedophile looks like. Why didn’t the kid go running to mummy as soon as he was groped? This is partly why so many victims take their shameful secret to their graves.

Leaving Neverland is a humble attempt to change that, and light a beacon for those who, when the time is right, may wish to break their silence and confront their abuser, alive or dead.