More than 4m copies have been sold (Donaldson's total sales have topped 14m), a stage show is in the West End, Gruffalo merchandise is in the shops, and last month Radio 2 listeners voted it the nation's favourite bedtime story, ahead of Winnie-the-Pooh. On Christmas Day a new 30-minute animation will be screened on BBC1, featuring the voices of Helena Bonham Carter and Tom Wilkinson. The Gruffalo celebrated its 10th birthday this year. 'At the beginning it was quite a naff idea, I thought,' Scheffler says, 'but I'll have to carry on now because children have started looking for it.' Since then, Donaldson-Scheffler fans have been able to play a game of spot the gruffalo: in each of their books, somewhere in one of the pictures lurks their distinctive brown monster – disguised as a fish, a Christmas decoration, a cuddly toy. W hen he was working on the illustrations for Julia Donaldson's The Snail and the Whale, a few years after their hugely successful picture book The Gruffalo, Axel Scheffler had the idea that one of the children on the beach in the story could be drawing a gruffalo in the sand.

The Gruffalo by Julia Donaldson