I did lots of research into world folk stories, and came across one about a little girl who went out into the jungle and was confronted by a tiger, which she then outsmarted. I thought it would make a nice little play; then I realised it was the germ of a good picture book.” Donaldson chewed the idea over for a couple of years. “It was a time in my career when I’d had only educational books and one trade book published. Roald Dahl had that problem with Charlie and the Chocolate Factory and, eventually, disassociated himself with the film.

I guess if Dr Seuss was alive, he wouldn’t be too happy with the current film of The Cat in the Hat.”The genesis for The Gruffalo came in the mid 1990s “It’s loosely based on an ancient story,” says Donaldson. We’ll see.”It’s like that with books that take off, reckons Michael Rosen “It’s a strange process,” he says. “It starts by someone reading your book in a way you don’t like, then slowly, but surely, it moves it out of your hands. “I didn’t want it to become a long-running Tom and Jerry-type cartoon, nor did I want the Gruffalo and the mouse to become friends, learning to count together or something like that. It’s a poem, like The Owl and the Pussycat.” She seems cautiously to approve of a recent idea to make a half-hour television show, like the perennial adaptation of Raymond Briggs’s The Snowman, but when a Hollywood studio got in touch – the idea being to make a blockbusting kids’ feature film – it put such emphasis on getting the rights that Donaldson and her publisher backed off. “I’d hate it to become like Winnie The Pooh, with other illustrations of the Gruffalo taking away the essence,” she says “But I’m not saying a film won’t happen.

“I was particularly worried about one, as they wanted to make it into 13 episodes, which would inevitably change the character of the Gruffalo,” says Donaldson. When three different television companies got in touch, each interested in filming the story, Donaldson was circumspect. But The Gruffalo is her magnum opus; her Sgt Pepper, her Ulysses.Donaldson, 55, is a writer and parent from Scotland who lived in the wilderness for ages, writing songs for children’s television. She was a songwriter for Playaway, and, although she had books published, she had periods in the doldrums: “I know what it’s like to sit there, unpublished.”In other words, she is equipped to cope with Gruffalo-mania. I love that poisonous wart on the end of its nose.” The children’s book expert Nicholas Tucker, a lecturer at Sussex University, says characters like the Gruffalo have a special resonance with children. “Writing about animals is always popular, and to come up with a new monster with a great name is really skilled, particularly as the monster is scary but also has a cuddly nature.”The Gruffalo has been translated into 26 languages. “As soon as we read The Gruffalo, we saw dramatic potential in it,” says Toby Mitchell, of the Tall Stories theatre company, which has its own production “It’s very simple and very concise.

We’re faithful to the book, and also appeal directly to the audience, who all know it off by heart.” The play is now travelling to the US and Canada.At her home in Glasgow, The Gruffalo’s author, Julia Donaldson, is delighted and even a little bemused by the success of her warty beast “Sometimes I feel the Gruffalo owns me,” she says. “It’d be lovely if people mentioned my other books.” Donaldson has also written The Snail and the Whale, Room on the Broom, Monkey Puzzle and more, several also illustrated by Scheffler. The Gruffalo is scary without being terrifying, and has great detail. “It fits together like a crystal, with all the facets in harmony.”Kate Wilson, the director of children’s books at Macmillan, publishers of The Gruffalo, says: “It works really well as a shared experience: adults like it as much as children. And, like a Zen master who has used his antagonists’ aggression against them, the mouse sits and eats a nut.