Towards the end of Philip Pullman’s His Dark Materials trilogy, a weary, decrepit God cowers in fear of his life, tears streaming down his face in terror.

Two children tower above him, their love for one another defying the malevolent wrath of organised religion.

This is hardly the usual stuff of Christmas drama. But in December a two-part adaptation of the trilogy will begin at the National Theatre. It is a radical departure from the venue’s recent run of lavish Christmas musicals, which never demanded too much from their festive-season audiences.

But Philip Pullman believes audiences will respond well to the challenge.

“My readers are very sensible people. They’re the cream of the crop,” he said. “They are capable of responding vividly and passionately.”

And Nicholas Hytner, who took over as director of the National in April, sees it as his role to question convention. “There’s always a hunger for large theatrical epics,” he said. “But old Victorian and Edwardian classics have had their day. I want to make theatre for kids, not adaptations of their grandparents’ stories.”

The anti-establishment fury of His Dark Materials, he believes, perfectly fills this brief: “Sure, it’s anti-clerical, but it is full of spiritual yearnings. It’s a hugely ambitious attempt to create a new mythology for a generation not served by organised religion.”

The Mail on Sunday once described Mr Pullman as the most dangerous author in Britain. Mr Hytner is dismissive of the media hysteria surrounding the novels. Contemporary audiences, he says, can handle occasional on-stage heresy. But he and his cast do fear other, different cries of heresy.

Children are notoriously territorial about novels that they love, and necessary adaptations and omissions could alienate the target audience.

“There’s concern that teenagers will be sitting there with arms crossed, saying it’s crap,” he said. “When you fail, it’s miserable.”

But actress Patricia Hodge, who will play villainess Mrs Coulter, says such fears are inevitable with any theatre adaptation.

“Even if you do Hamlet, you’re up for comparison,” she said. “The audience have to understand that this isn’t the book. This is something else. It’s Philip Pullman’s ideas and theories put on to the stage.

“You can’t portray what’s in somebody’s mind. But you invest in the characters. Hopefully any omissions will make the whole moral, philosophical and religious debate going on at the heart of the story far more colourful and immediate.”

Talk like this is enough to give most authors palpitations. But Mr Pullman has been notably sanguine about the public carving-up of his most famous work. He sees the theatre production as a critical test of his own abilities as a writer. If the central story is strong, it will stand up to telling through an alternative medium.

“I’m a book person. They’re theatre people,” he said. “I think the best thing for me to do is keep out of the way and make encouraging noises.” The presentation of the familiar in unfamiliar form might also encourage children to experiment further with the theatre. “The theatre gives children another language, another mode of expression. It’s a collective experience. We join in, we laugh, we clap, we cry. We’re part of a total emotional link,” he said.

But, he believes, pressure to meet government targets has meant that heads are reluctant to allow pupils to capitalise on this experience, by organising theatre trips and workshops.

“You’re constantly having to struggle against the perceptions of some people in education, who think theatre is a luxury. They think it takes time away from tests and other important things, letting results slip. It’s such a morally and emotionally poverty-stricken way of looking at education.”

His Dark Materials previews at the National Theatre from December 4. Box office: tel 020 7452 3000.

PARALLEL LIVES NEVER DEVIATE

Philip Pullman’s His Dark Materials is made up of three books: Northern Lights, The Subtle Knife and The Amber Spyglass.

The trilogy tells the story of two children, Will, who lives in our world, and Lyra, whose world exists in parallel. When children, among them her friend Roger, begin to go missing in Lyra’s world, she sets out to find them. Travelling back and forward between different worlds, Lyra meets Will, who agrees to help her in her search. Together, they encounter armoured bears, witches, soul-eating spectres and rebellious angels, as they struggle to come to terms with their ownidentities. But it is only, ultimately, by battling with God and the grasping powers of organised religion that they are able to discover their own capacityfor love.