The new Disney movie, Saving Mr Banks, which opens on Friday, is more audacious than any film has been for a long time.
It tells the story of PL Travers, author of the six Mary Poppins novels that most people haven't read, and her battle with Walt Disney over the film that everyone's seen.
Travers hated the 1964 musical Mary Poppins (or, as it was officially and not wrongly called, "Walt Disney's Mary Poppins").
She had never been a fan of the great showman or his studio. In her early work as an arts critic, she reviewed Snow White and wrote of Walt Disney: "There is a profound cynicism at the root of his, as of all, sentimentality."
For 20 years, she refused to sell him the film rights to her novels, for fear that he would sentimentalise her chilly, dark tales of Edwardian nursery life. She eventually caved in and saw her nightmare realised in the finished film: cartoon penguins, happy endings and far too many spoonfuls of sugar.
With what chutzpah, then, does the Disney Corporation, nearly 50 years later, make a film about that very negotiation itself?
My word, she'll be turning in her grave at the latest development. Saving Mr Banks reveals the difficult Australian childhood that Travers sought to obscure (changing her name and accent, along with her geographical location) and tells that story with tear-jerking sentimentality. It's a wonderful movie – but so was Mary Poppins, and that made no difference to Travers. She hated it anyway.
Her only consolation, as she spins wildly beneath the ground, is that Saving Mr Banks finds no room for her intriguing personal life as an adult: it says nothing of the complex romantic relationships and bizarre attempt at adoptive motherhood that she also wanted to hide.
Unfortunately for the former Helen Lyndon Goff (and I would genuinely apologise if she were standing next to me), I've been working on a documentary, due for broadcast this Saturday, which tells those stories too.
I'd apologise because I feel very sympathetic to her side in the Disney row, although I don't think Saving Mr Banks means us to. It is full of compassion for her personal trials (she is played by Emma Thompson, perhaps the most likable and affecting actress in history), but, when it comes to story-telling, the new movie is squarely on the side of the Disney approach: sweet songs and emotional resolution.
Travers was wrong about Walt Disney's Mary Poppins and its unforgettable score. She didn't understand the medium, nor why it needed to be neater and sweeter than her shady, jagged stories in order to have the power it does.
But I love her for defending the principle of darkness in children's fiction and admire her enormously for sticking to what she felt was right. It's brave and difficult for a woman to fight her corner in a male-dominated workplace now, never mind in 1964. How ironic that Walt Disney reinvented the character of Mrs Banks as a suffragette, yet expected instant and docile submission from her creator.
PL Travers had a complex nature, but I think what fascinated me most, while working on the documentary, was this issue of control.
She wanted to control everything about her creation. When the first book was accepted, Travers hurtled up and down from London in her sports car, arguing with publishers about artwork and typefaces. When Disney's film version was under way, she wanted to design the sets, choose the costumes and tweak the songs – even though she didn't want songs at all.
And yet, when she decided to adopt a child, she chose her baby on the advice of an astrologer. It's hard to think of a more extreme way of relinquishing responsibility.
The child, Camillus, was deeply damaged by some of Travers's subsequent terrible decisions (including keeping the adoption secret; he discovered it by chance, aged 17, in a pub), but her granddaughter Kitty told me that Travers felt no guilt because: "She thought it was all written in the stars."
I don't know if PL Travers was familiar with the Serenity Prayer, but when it came to "the serenity to accept the things I cannot change, the courage to change the things I can and the wisdom to know the difference", she had it all upside down.
It seems so odd that she sought complete professional autonomy, unable to collaborate happily with other people – she never accepted that any colleague might have a better idea about any aspect of a work in progress – and yet lived quite certainly with the belief that stars and planets dictated everything anyway.
She tried to overrule everybody, trusting only herself, despite seeing fate as a total determinant that left her ultimately powerless.
So odd and yet, in a way, so recognisably female: not in the specifics, but in the ongoing struggle to know where and how to exercise power. It's why teenage girls suffer from anorexia: seeking absolute control in one area to compensate for a feeling of impotence everywhere else.
Will it always be like that? Will another 50 years of suffrage make any difference? Does it come from centuries of oppression; or is it biological, a sort of metaphor for motherhood? Is serenity achievable?
I know this much: while making the documentary, as I busily rewrote bits of script, suggested locations, worried about plane noise and changing light, advised the cameraman on angles and sternly told the director what I thought the ending should be, I prayed they would be thinking: "It's nice that she cares", rather than: "Christ, it's no wonder she sympathises with the old battleaxe she's talking about."
Chances are it's all a bit of both.