What is it about Dahl that we loved then, now and all the years in between?

At its most basic level, it is simply that Dahl is a wonderful, natural storyteller. You can see it in him even as a child in his letters to his mother from boarding school. The same economy and vividness with which he conveys the results of a roller-skating adventure (“I sat down in the middle of it. My bottom is all blue now!”) infuses everything he ever wrote. Remember the very first pages of Charlie And The Chocolate Factory, when the author addresses you directly – “This is Charlie. How d’you do? And how d’you do? And how d’you do again? He is pleased to meet you”? That’s Dahl reaching out from the pages, hitching you up and pulling you into the story with a swiftness and confidence that only increased as his career went on. I remember particularly my teacher reading The Witches to us at primary school and having to say that witches could be anyone, even “your lovely school-teacher who is reading these words to you at this very moment”. Oh, the unspeakable thrill of such transgression!

As a child you could sense that Dahl understood you, even without knowing that he once resigned from a national educational committee when they refused to read Enid Blyton’s works in schools due to concerns about xenophobic sentiment. He argued that children loved Blyton’s books and she got them reading. He was a writer firmly on the side of the child and you could feel it on every single page.

Yet Dahl has had his fair share of detractors too. After all, his books deliver a good dose of anarchy – the Twits mindf***ing each other, George mixing his grandma’s well-deserved toxic medicine – for the young mind. His critics used to hate it. He was often accused over the years of being too violent, too sadistic and too altogether vulgar. The characterisation of a child suffering at the hands of twisted, cruel adults cropped up again and again in his work: Matilda was subjected to the cruelties of sadistic parents and teachers while James of Giant Peach fame was orphaned after a rhino killed his parents and sent to live with his evil aunts. Yet the vulnerability of children was a core concern of Dahl, who himself lost his father and sister at a young age before being sent to boarding school where he was repeatedly beaten.

An early reviewer of James And The Giant Peach was appalled by the “violent exaggerations of language” and its gross characterisations. Fellow children’s writer Eleanor Cameron condemned Charlie as “one of the most tasteless books ever written for children… like candy [it is] delectable and soothing while we are undergoing the brief sensory pleasure it affords but leaves us poorly nourished with our taste dulled for better fare.” By the Eighties and Nineties, the charge of misogyny was being laid at Dahl’s door – George’s grandma was treated too cruelly, Miss Trunchbull was a negative portrayal of spinsterhood, and a book called The Witches didn’t deal in wholly positive versions of femininity either.

But there have always been enough readers and critics to see that Dahl’s books are modern fairytales. They – and their violent moments – are not to be taken literally. Charlie’s rags-to-riches story is, like Cinderella’s, a promise that whatever your besetting problem is – from intractable maths homework to divorcing parents – it, too, shall pass. Dahl’s ‘vulgarity’ is the equivalent of the broad, bright strokes in which the classic fairytales are painted. The ‘sadism’ is part of the tradition of extremes the form requires. “In writing for children,” says Dahl, “You have to exaggerate a million times in order to ram the point home.” As for the misogyny, Dahl the writer hates adults generally, rather than women specifically. In real life things were possibly a bit more complicated (I think he had a good dose of misanthrope in his make-up and a few beliefs about women that would seem unenlightened to us but were standard-to-liberal for a man of his class and era). For every Trunchbull or witch, after all, there is a Miss Honey or heroic grandma. Child heroes can be called Charlie or Sophie, Danny or Matilda. The male and female Twits are equally vile.

“Once upon a time…” Lucy Mangan explores our enduring love of Roald Dahl