I created a monster: Julia Donaldson on how the Gruffalo has taken over her life

If the Gruffalo, with its warts, bad teeth and jaundiced eyes, has seemed inescapable recently, then it is with good reason.

The children's picture book written by Julia Donaldson and illustrated by Axel Scheffler, celebrated its 10th anniversary this year, an occasion marked in bookshops and school assembly halls up and down the country for months on end. The stage show, which has been in repertory since 2001 – not just in the UK, but across America, Chile, Singapore, Hong Kong and Australia – is about to transfer to London's West End for the duration of the Christmas season.

And on Christmas Eve it will be one of the BBC's seasonal TV highlights as a half-hour animated special, voiced by Robbie Coltrane, Rob Brydon and Helena Bonham-Carter. The listeners of Jeremy Vine's Radio 2 show, meanwhile, recently voted the book the nation's favourite bedtime story. And there came further proof last month of just how far the tale has now seeped into global consciousness when our incumbent Prime Minister was referred to as the Gruffalo of modern politics. (Need one point out that this was not a compliment?)

But on an overcast November afternoon at her home in Glasgow, the author herself would, quite frankly, rather talk about anything else than the book which has sold four million copies around the world.

She sighs, slowly and evenly. "This is all going to be about The Gruffalo, I suppose?" she begins as we sit down and prepare to chat. Julia Donaldson is a well-preserved 61 years old, but has about her a rather distracted air.

Would she rather talk about something else, I ask.

"It's not that, it's just that this is the only book journalists ever want to know about. I have written others, you know."

She mentions, specifically, Running on the Cracks, her first novel for teenagers, which was published earlier this year to critical acclaim, if not quite national fanfare. "What I do find frustrating," she says, "is that you can work away for a year on a book like this and still..."

The sentence remains unfinished, Donaldson perhaps aware that she should keep these frustrations private. It sounds, I say, as if she has begun to resent the monster that has made her so famous and wealthy.

Another sigh. "No, I don't really resent it because – well, let's face it, I think any author would love to have some iconic character they can pin everything else on. But all the things I keep talking about these days I've heard myself talk about before. So I'm not learning anything new, am I?" She frowns. "Imagine if you had written an article 10 long years ago, and all everyone ever wanted to do was keep on bringing it up, even though you had written lots of perfectly good articles since. The Gruffalo seems to overshadow everything else I do, at least in the media. But many of my books, you know, have sold just as well." They've all shifted a whopping four million copies? "Well, no, maybe not," she reluctantly concedes, "but many of them are hot on the heels."

So which of her books would she have rather had this remarkable success with? She thinks about this for quite a while, and her frown deepens. Her answer, when it comes, is quietly resigned. "I suppose I have to admit that I probably think The Gruffalo is... well, it has the best storyline. So, yes, it probably is the best one, isn't it?"

'The Gruffalo' is a David and Goliath story for fans of Davids everywhere. The story concerns a mouse making his way through a wood while avoiding becoming dinner for a variety of prowlers – fox, owl, snake – by employing the kind of cunning one wouldn't necessarily expect of a mouse. He endeavours to put off his would-be devourers by claiming the imminent arrival of a most fearful creature called the Gruffalo. The Gruffalo doesn't exist, of course – until, on page 14 of 24, it suddenly does. It's a hungry one, at that, requiring of the mouse yet more cunning if it hopes to escape.

That it shrewdly does is what makes this such a charming story, and beautifully illustrated too, by Scheffler, a ' 52-year-old German artist who has resided in London for almost 30 years now, and who has collaborated on many of Donaldson's most successful picture books.

Scheffler lives and works in a small, triumphantly messy flat in Blackheath, south London, which he shares with his French partner, and their two-year-old daughter. A breakfast bowl full of freshly brewed coffee in his hands, he shows me into his studio, which is strewn with notebooks, pens and papers, oozing paint tubes, bits of old newspaper, and at least one stuffed Gruffalo toy, alongside piles and piles of books. One that hangs on for dear life to a corner of his overflowing desk is the just-published Iranian version of the tome that will ensure his drawings will live on forever.

"When I think of just how successful it has been," he says in his perfect, whispered English, trying to find an uncluttered space for us to sit, "it almost scares me. It's baffling. The book is everywhere. I try not to think about it too much."

The writer and illustrator have been working together since A Squash and a Squeeze, the book that, in 1993, rescued Donaldson from a life of part-time teaching and writing children's songs for kids' TV, which she had been doing since the late 1970s. Before that, Donaldson had wanted to become a folk singer, and she and her husband, Malcolm (now a paediatrician in a Glasgow hospital), spent several summers in their early courtship busking on the streets of London and Paris. Following their marriage, she became a largely stay-at-home mother to three boys, now restricting herself to occasional performances at student balls and corporate functions.

"If we were asked to do a dentist's convention, for example," she says, "I'd write songs about teeth. It got to the stage where I could pretty much write about anything on demand."

A Squash and a Squeeze is the tale of an old woman who complains about her cramped house until a wise old man instructs her to fill it with animals and then remove them to reveal far more space than she had first realised. It was written as a rhyming ditty for Playschool back in the late 1970s, and over a decade-and-a-half later, a commissioning editor at a children's publisher asked if she could turn it into a book. Donaldson was paired with Scheffler, and they have since worked – separately, she in Glasgow, he in London – on several hugely popular picture books, among them Room on the Broom and Stick Man, both of which have also been turned into theatrical productions in time for Christmas.

Their creations have come to dominate their entire lives. Donaldson and her husband now spend so much of their year playing to children up and down the country, reading stories and singing songs, that her husband has taken early retirement in order to dedicate even more time to the process. Demand for personal appearances can be staggering: her last book signing went on for almost five hours. (Scheffler, a methodical artist who likes to take his time over his illustrations, is slightly less keen to reinvent himself in the role of children's entertainer: "I occasionally play the owl in some of Julia's shows, it's true," he says. "Do I enjoy them? If I don't have to do them too often, yes.")

"The fame, if you want to call it that, is nice," Donaldson admits, "but it has made me feel I need to be on my best behaviour at all times, just in case. It wouldn't do to have a row in a supermarket, would it? People may recognise me."

But while she enjoys entertaining her readers, she is less enamoured by her occasional dealings with the press: "I did do some recently, but mostly all people want to talk about is my son's death. They are obviously more interested in death than they are children's books."

In 2003, her older son Hamish, who suffered from schizo-affective disorder, committed suicide. Though she was loath to speak about it publicly – and mostly didn't – she did break her silence a couple of weeks ago on Desert Island Discs, which promptly re-opened the floodgates, "people wanting me to write columns and opinion pieces. But I really don't want to talk about it, and I won't again," she says decisively.

And so we talk instead about the BBC's adaptation of her book, which is already generating much advanced praise, not least from herself: "I love it, which surprised me because I'm normally very critical about these things." She lowers her voice. "Though I have to say, it is terribly scary."

But then, scary is, of course, a staple of children's books. From Maurice Sendak's Where The Wild Things Are, which bewitched a generation of children while simultaneously giving them nightmares (and will do so again, as Spike Jonze's updating of it is about to reach cinema screens), to Roald Dahl's reliably macabre tales, many of the best children's stories have taken great pains to introduce their young readers to fear. The Gruffalo continues this tradition, though if Scheffler had had his way originally, the monster would have been even more gruesome. He shows me early sketches for it, which reveal a boggled-eyed hunched troll with a plainly murderous leer on its hideous face. The later, approved, version that graces the book has a far more friendly (if gormless) smile.

"I personally never set out to terrify children," Donaldson tells me, "and I hope I mostly don't. Though as I have found out since, some children do get scared by the slightest things, don't they?"

Is there no end to the inexorable rise of The Gruffalo? Oh yes there is, insists its creator. Enough is enough. So, unlike Harry Potter, there will be no accompanying theme park, and certainly nothing as crass as a film version.

"We've had offers," she reveals, "but I wasn't ever tempted. To me, The Gruffalo is essentially a poem. Nothing else. If there had been a Hollywood version, I'm sure they would have made up some mad story about them being in New York or something, and that wouldn't have appealed at all. Besides, I really can't understand why everyone is so thrilled by wanting to be on the big screen. Films have such a short life; they are so ephemeral compared to books, no?"

The usually reliable response to this sort of argument, of course, would be that more people go to the cinema than ever read books. But this is not the case with this book, which has already been published in more than 40 countries. Donaldson, then, has every right to be sniffy about anyone trying to take her creation and diluting it. But if she'll never entirely be able to escape its shadow, then she shouldn't complain about it too much. How many other people have managed to capture the world's imagination, after all? And not just childrens', either – parents love her stories, too. Her books are as entertaining to read as they are to listen to, and thus she has made bedtime routines so much less protracted and painful than they otherwise could so easily be. Parents everywhere are terribly grateful. She realises this, yes?

At last, she smiles, warmly. "Of course," she says. "And that pleases me, it does. I mean, how couldn't it?"

'The Gruffalo', the Apollo Theatre, London W1, to 17 January. The animated version is on BBC1 on Christmas Eve. 'The Gruffalo and Friends Show' with Julia Donaldson and the Gruffalo, to raise money for Prader-Willi syndrome, is at 1.30pm and 4pm, on 10 January, at Oran Mor, 731-735 Great Western Road, Glasgow, tel: 0141 357 6221, www.oran-mor.co.uk