On set to see Dahl's first children's story, James and the Giant Peach, turned into a film for Disney, the moment seemed to her to have a quality that her father strove to achieve in his writing. "He taught us that magical surprises are everywhere," she says. "But best of all is when you actually see magic - which we did the day the peach broke free and rolled down the hill." (Luckily the magic extended to having the peach stop just before crushing Joanna Lumley and Miriam Margolyes, playing the two wicked Aunts "Spiker" and "Sponge", in their car.)
Thanks largely to the insistence of Dahl's family, the film is true in most important respects to the 1961 original. It combines live action - supplied by Lumley, Margolyes and new English child star discovery Paul Terry - with the stop-action animation for which Selick became famous in The Nightmare Before Christmas.
When my children and I saw it at its New York opening in April, the audience gasped in wonder (at the imaginative perspectives and integration of actors and animated creatures), gaped in horror (as a rhinoceros comes out of the clouds) and cheered (when James arrives at his dream destination - New York).
For those who don't know the story, or need reminding, it's about a little English boy whose parents are (according to his wicked aunts) killed by a rhinoceros. He lives a Cinderella-like existence with said evil relatives until one day some magic comes into his life and causes a peach in the garden - and many of the creatures around it - to grow to gigantic size.
The aunts try to capitalise on the giant peach, but it has other ideas, rolling over them and out to sea, carrying James and his anthropomorphic insect friends away from their cloistered, claustrophobic existence to a brave new world of adventure and acceptance that James has dreamed about - in a kinder, gentler post-Second World War Manhattan that was so many immigrants' ideal.
Dennis Potter was initially commissioned to write the script. "Potter was my idea and I'm proud of it," Selick admitted during a brief sojourn in London, "because his work is astonishing in its progression from reality to fantasy. But I guess he took it too far away from Dahl. He set it in World War II with Nazis and has James's mother killed in the Blitz with his father coming back to get him in the end, whereas this is really about a boy who survives his loss of family and finds a new one."
Dahl's widow, Felicity - who retained an authority over the proceedings that is almost unprecedented in Hollywood history, only selling the film rights with strings such as "script approval" attached because she was determined her husband's work should not be altered or sentimentalised out of recognition - remembers it slightly differently.
"When I heard they'd commissioned a screenplay from Dennis Potter, I gasped and said, 'You must be mad!' They said, 'Oh, we thought you'd be delighted because he was English', but I thought Potter and Dahl would be adisaster, as it proved. The script arrived with Vera Lynn, Nazis, U-boats, the works. It had to be ditched. But they'd paid a lot of money for it."
Henry Selick takes up the tale. "We then went to Jonathan Roberts, who'd worked on Lion King for Disney. No one loved that script, but it was close to the book. At that point the plug was almost pulled on the project, until two writers were commissioned at the same time to have another try. One was Bruce Joel Rubin, commissioned at a very high price. The other was an unknown called Karey Kirkpatrick.
"Bruce Joel Rubin ignored the book and turned it into The Wizard of Oz - making it all a dream. But Karey's work was true to Dahl and both Liccy (Felicity Dahl) and I loved it. We suddenly found ourselves allies against the powers that be. There came this fateful day when Disney told me how much they'd warmed to Bruce Joel Rubin's script, and how much they'd paid for Bruce Joel Rubin's script, but Liccy and I fought for Karey Kirkpatrick's and won!"
Although Selick calls his relationship with Mrs Dahl and the Dahl Foundation "collaborative", it is clear that considerable diplomacy was necessary. "She wasn't happy with some of the changes we had to make," he reveals. "She was happy with the Aunts returning at the end - because we felt we needed them to provide an antagonistic pursuit, whereas in the book they get flattened by the peach.
"But she was upset that we had to eliminate the Cloud Men - and I understand that. But they were just too much. And she wasn't happy with what we did with the rhino." The rhino is a recurringly terrifying image who comes out of the clouds, and "had to be scary", Selick insists - despite the risk of frightening some small audience members.
The film makes use of virtually every type of animation technique available including computer-generation, which caused such a sensation in Toy Story. Although it took two years and a team of 130 to create, Selick triumphantly points out that "Toy Story took four years."
For Selick, stop-animation - in which puppets are created out of metal skeletons baked into latex rubber forms, and painstakingly posed by puppeteers - is not only currently a cheaper option, but is also a superior tool. "I don't see us trading in this very special craft just to sit at terminals like other people," he says. "I find stop-animation has the most appealing, tactile quality, which you don't get in computer animation. Computer animation may have more surface gymnastics, but it doesn't convey the same weight of personality and emotion. The ocean in James was generated by computer, and looked like toilet-bowl liquid at first."
Selick, 43, and bearing a slight resemblance to Jack Skellington in The Nightmare Before Christmas in that he is tall and thin with a high forehead and sharply chiselled features, has had a long apprenticeship in stop- animation at Disney. He only directed his first feature film, Nightmare, in 1993, after having worked for 18 years previously as an animator on Pete's Dragon, The Small One, The Fox and the Hound, The Watcher in the Woods and Return to Oz.
Born in New Jersey, a graduate of CalArts and now a confirmed Californian, Selick was inspired in his youth by the work of Ray Harryhausen, the father of modern stop-motion animation in the Seven Voyages of Sinbad and Jason of the Argonauts adventure films of the 1950s and 1960s. "King Kong was really the first good example, so it goes back a long way," Selick notes. "You just need a lump of clay, some wire, sone tinfoil or your old doll and you can bring things to life with very few resources," he enthuses. Nevertheless, Nightmare was the first big-budget, Hollywood stop-animation film, according to Selick, and James is only the second.
It was at Disney that Selick met James co-producer Tim Burton, who also devised and co-produced Nightmare Before Christmas. Felicity Dahl remembers how it was being flown over to Hollywood by Disney to see Nightmare in the making that convinced her to let James be made into a film, despite her late husband's disillusionment with previous film attempts at his work, such as Charlie and the Chocolate Factory and The Witches.
"When I first met Tim Burton, I nearly had a fit, because he looks so like his creation Edward Scissorhands!" Mrs Dahl recalls. "I asked him why he wanted to do James. He said, 'It's the only thing that gave me any hope as a child.' And I was seduced!" So were stars such as Susan Sarandon, Richard Dreyfuss and Simon Callow, who lent their voices to Spider, Centipede and Grasshopper respectively.
One problem with having worked so long with animation is that he wasn't exactly an actor's director. "In animation you plan so much and can be very controlling. I wanted to block in Joanna [Lumley] and Miriam [Margolyes] like the puppets. But they soon disabused me of that idea, and I had to learn to wait and let them show me what they could do."
While promoting James, Selick is hard at work on other projects. "I'm in business with Miramax, a subsidiary of Disney, developing Toots and the Upside Down House, a new book to be published later this year by Carol Hughes, a 'British transplant' in LA. It will also be a blend of live action and stop-action animation. And I'm developing another based on 'Slow Bob', a character I devised in 1990. He'll be in a land of monsters, with a lot of black comedy."
His face, Hollywood director-inscrutable behind gold-rimmed spectacles, becomes more animated merely at the thought.
n 'James and the Giant Peach' is released on 2 August