There's a story Philip Pullman tells to illustrate what he's about. Many years ago, on holiday, he decided to amuse his five-year-old son, Tom, by giving him a version of the Odyssey every night. 'By the end of the story, Tom, who was sitting with a glass in his hand, was so galvanised he bit a chunk out of the glass. That's the power of storytelling. Thank you Homer.'

The author of The Amber Spyglass likes to place himself in the oral tradition, and is only too happy to acknowledge literary forebears such as Milton, Blake, Swift and Dickens. To Pullman, stories are simply part of our collective inheritance. 'What I am given is the story. What I have to contribute is my telling of it.'

Everything about Pullman's childhood contributed to the making of a master storyteller. He was born in Norwich in 1946, son of an RAF fighter pilot. He and his younger brother were living in southern Rhodesia when Pullman senior was killed in action, flying a sortie against Mau Mau terrorists in Kenya. Philip was just seven years old.

His mother's remarriage took him to Australia in the 1950s where he discovered Batman and Superman, and became liberated from English fictional models. In an uncanny echo of JK Rowling's Harry Potter, this late child of empire then found himself shipped home to an English prep school, a voyage that inspired a taste for epic worlds.

Like many children sent away to school he found an emotional anchor in his grandfather, a Norfolk clergyman, who 'took us to church on Sunday and told us Bible stories'. At school, he acquired the habit of improvising stories, of finding comfort in a parallel universe that's stayed with him ever since. He retains the slight detachment of the fatherless boy. And having lost faith in Christianity he has sought an alternative in the adjacent world of his fiction.

After reading English at Oxford, Pullman stayed on there, working briefly for Moss Bros, and then as a librarian. Later, he trained to become a teacher. Some of his utterances to the press in recent years have had the didactic contrariness of the ex-schoolteacher.

From 1972 he taught pre-teenage children at two Oxford schools. He also wrote school plays. The distinguished children's author-illustrator Shirley Hughes comments on the 'extraordinary range of [Pullman's] reading in mythology, literature and the Bible'.

Pullman adapted some of this storytelling into fiction. He learned that it was possible to make what Hughes calls 'this incredible demand on the reader' and - if the narrative was right - to get away with it. In the aftermath of winning the Whitbread Prize, Pullman told The Observer that his audience 'does not consist just of children, but does of course include children'. The inferior status of the children's book writer in the English literary class system plainly rankles.

In 1983, having published two unsuccessful novels, Pullman completed a 'pastiche Victorian thriller', based on ideas he had explored as a teacher. His agent sent it to David Fickling, a young editor in the children's department of Oxford University Press. 'I read it at one go,' Fickling recalls. 'It was as good as Wilkie Collins. And it had what his work always has, which is an amazing economy - the best result by the shortest route.'

The Ruby in the Smoke (1985) established Pullman as a children's writer to watch. Then came Northern Lights (1995 - later The Golden Compass), the first volume in a projected trilogy which, taking title and inspiration from Milton, Pullman christened His Dark Materials. This, says Fickling, was 'unbelievably original... and if the world didn't think it was amazing, I should have been very surprised.'

Pullman's trilogy contains many of the familiar elements of fantasy and adventure novels: juvenile heroes who undergo life-threatening and character-forming trials; an epic struggle between good and evil; love and hatred; and a cliffhanging narrative.

His work is bursting with big ideas and with answers to his passionate demand that children's literature should be about grown-up things: Where did we come from? Where do we go? What is our purpose as human beings, and how should we conduct our lives?

Pullman also gives his readers angels of immense spiritual purity who happen to like Kendal Mint Cake, tiny creatures called Gallivespians, nice witches, and (his most celebrated invention) 'dæmons' - the outward manifestation of our inner lives in animal form.

He exposes his characters to page-turning adventures. 'Children aren't interested in irony and cleverness,' he has said. 'They want the story, what happened next.'

But the early Nineties was not a good time to be writing for children who, it was widely held, were only interested in video games and cartoons. Pullman achieved his first big moment of recognition, with the award of the Carnegie Prize in 1995.

It was then that he broke cover, accepting the prize with the widely-quoted assertion that 'only in children's literature is the story taken seriously'. Pullman's undiplomatic candour (what some have described as 'a mixture of charm and awkwardness') is the residue of his years in the literary wilderness.

While the as-yet-uncompleted trilogy grew in reputation, the literary tide turned in favour of writers for children. Rowling achieved her astonishing audience; Tolkien was rediscovered; and Pullman became published in America (where he is known as an author for adults), and France and Germany (where he has a huge readership). He could afford to give up teaching and devote himself to The Subtle Knife (1997) and then The Amber Spyglass (2000).

The latter has sold several hundred thousand copies, but Pullman still lives in Oxford with his wife, Jude, and their two sons. He writes, like Roald Dahl, in a shed in the garden. He works in silence, drafting and redrafting each sentence until he's got it just right.

And just as Tolkien created 'The Shire', an idealised version of the English pastoral, so Pullman's imaginative world reflects the atmosphere of 1970s socio-political crisis in which he first began to write. His favourite character, the deliciously villainous Mrs Coulter, owes more than a little to Mrs Thatcher.

Goodness, and the related theme of tolerance, is a subject that fascinates him. As his trilogy unfolded he has developed his ideas about a 'Republic of Heaven', a place of joy and delight, and the promise of connection with something beyond ourselves. 'We all need some sort of myth,' he has said. 'Some sort of over-arching narrative to live by. For hundreds of years in the West, this need was fulfilled by the Christian story, but that is now either dead or dying.'

It is Pullman's anticlericalism that caused the Catholic Herald to denounce his work as 'truly the stuff of nightmares... worthy of the bonfire.' He counters with 'Look at the whole story... Is it celebrating love, kindness, open-minded curiosity? Is it condemning cruelty, cold-heartedness, fanaticism? Yes it is.'

Since the publication of The Amber Spyglass, Pullman has stepped up his assault on CS Lewis, accusing him, with some justification, of 'misogyny, racism and a sado-masochistic relish for violence'. In turn, he has found himself enthusiastically adopted as a myth-maker for 'the children of a faithless age'.

Friends and fellow-writers don't wholly recognise this. To Shirley Hughes, he's a writer 'of extraordinary descriptive power' whose 'work will surely live for ever like all the finest children's writing... The thing is that he's terribly visual. He draws on the tradition of grand narrative and simply nothing can match the power of his imagination.' In this, he owes a debt to another literary and artistic hero, William Blake, a writer who famously once said he saw a tree 'starred with angels'.

It's the quotidian dimension to his imagination that makes his work of such interest to contemporary readers. Like Lewis, he gives us a parallel world, but unlike Lewis it's a 'multiverse' fraught with doom, dysfunction and despair, a vision of society drawn from the pages of Gustave Doré, one of his favourite artists.

Pullman himself makes an unlikely demon. In person, he is thoughtful, good-natured and passionately interested in what the world has to tell him. Like his admired predecessors, he is only giving back to his audience the stories it has already vouchsafed in a thousand unguarded moments. First and foremost a teller of tales, he acknowledges 'the absolute preciousness' of reality in all its chaos and discomfort. 'Here is where we are,' he told The Observer, 'and now is where we live.' It was this deeply rooted, practical Englishness that the guests at the Whitbread Prize were applauding on Tuesday, a storyteller for the tribe.

Born: 19 October 1946, Norwich
Family: Married to Jude; two sons, Jamie (a viola player) and Tom (a music student)
Job: 'I write stories'
Office: The garden shed (which he shares with a 6ft-tall stuffed rat)