AT FIRST, EVA GREEN WAS quite intimidated by Philip Pullman. “Well, wouldn't you be?” she asks with an English accent that barely has a trace of her Parisian roots. “The man is a genius and when you meet him he's like an academic, a don or something...”

Green, best known for playing Vesper Lynd in the last James Bond movie Casino Royale, joined a stellar cast — including 007 himself, Daniel Craig, as Lord Asriel and Nicole Kidman as Mrs Coulter — in the director Chris Weitz's big-screen version of Pullman's book The Golden Compass (published as Northern Lights in Britain).

Pullman, a frequent visitor to Shepperton Studios, was apparently happy to stand on the sidelines and watch proceedings. “The first time I met him he knocked on my dressing-room door,” recalls the 27-year-old Green, who plays the 400-year-old witch Serafina Pekkala. “I opened it and he was standing there and said [adopts deep voice]: ‘Let's talk about Serafina...' I thought: ‘Oh my God, does he think I'm going to be all right?'

“But he was lovely. He's very articulate and very enigmatic but he's a sweet man and I hope he won't be disappointed. He was like a child and kept saying ‘Oh I love that scene...' It must be amazing when you are the author and you see your words come alive in front of your eyes.”

It must indeed. Although Weitz, a Cambridge-educated American, faces the far more daunting task of pleasing not only Pullman, but the army of fans of his trilogy His Dark Materials, and a studio, New Line, which has invested more than £75 million in the project and is planning two sequels if the first film is a success.

Weitz, 38, was making About A Boy in London in 2002 when a friend suggested that he read Pullman. “I loved the scope of the books,” he says. “They are incredibly ambitious and by the third book they kind of expand into this vast Miltonic scale. It was great storytelling and it was clear it wouldn't be a problem to adapt.”

He's right. At the heart of The Golden Compass is a great adventure — a young girl, Lyra, who believes she is an orphan, is raised among academics in an imaginary Oxford where she runs wild with the street urchins and gypsy children.

When numerous children are kidnapped — including Lyra's friend Roger — by a sinister group known as the Gobblers, rumours abound that they are being taken to the North, where they are they are subjected to grisly experiments. Lyra vows to rescue them.

All well and good, but bringing Pullman's exotic characters to life on screen — human beings whose souls manifest themselves as animals (known as daemons), flying witches, talking bears — and surreal cityscapes of London and Oxford and the North Pole, was another matter.

Weitz was well aware of this, of course. He signed up to direct only to announce a few months later that he had resigned. “The technical challenges of making such a project are more than I can undertake at this point,” he said in 2004.

There would be another director, Anand Tucker, briefly attached and a Tom Stoppard screenplay commissioned before Weitz came back on board in early 2006 and wrote his own screenplay. He has obviously changed his mind about those technical challenges.

“We are on the very edge in terms of what we can achieve with the visuals in this film,” he says. “It couldn't have been done before in terms of what the audience expect.” The actors spent a lot of their time acting in front of a green screen — basically a blank canvas to which computer generated images, daemons, talking bears, airships, are added in the editing suite.

“It can be a bit strange,” the 13-year-old Dakota Blue Richards, who plays Lyra, says. “There wouldn't be anything there except maybe a stick with a little ball on it and you would have to pretend that it was an animal or something. And sometimes they got an actor to dress up so that you had someone to say the lines to.”

Craig also had to do his stint in front of the green screen but, he says: “Chris and his team also built some fantastic sets at Shepperton and we did some wonderful location work on the mountains in Switzerland.”

There was another challenge for the director. Before filming started he managed to raise a few eyebrows by commenting that the film would play down references to the Church and religion.

This is one of the most controversial aspects of Pullman's book, with its philosophical themes about spirituality wrapped up inside a cracking good yarn. The Church is behind the plot to kidnap and experiment on children and is out to crush individuality and freedom.

Cynics feared that a studio with its eye on the box office wouldn't want to risk alienating Christian groups with such content.

At the time of writing, the finished film had not been screened. A ten-minute preview was shown at the Cannes Film Festival and looked fantastic but it was impossible to tell exactly how Weitz had tackled the anti-dogma themes.

“I don't think Philip Pullman is an anti-religious writer,” the director says. “But I think he doesn't like structures of authority and, directly, the film addresses that stuff. I don't think it's the kind of movie that would offend a Christian, a religious person. But at the same time I think that people who love Pullman's books because of their iconoclasm won't be disappointed.”

Pullman still hasn't made his view clear on the film treatment. But he has obviously been a strong supporter of Weitz and his cast, with regular trips to the set and a visit to the Cannes festival. For the director, Pullman was simply the most valuable resource of all.

“It was a lot of fun for me because he is one of my favourite authors,” Weitz says. “I e-mailed him before I even got the job when I thought I would “clear” it with him. Did he want a movie made? What kind of movie did he want? What mattered to him?

“You can either be scared of your living authors or you can try, because you love the books, to embrace their choices as much as possible and take their guidance about how you are going to go about translating their work. As it happens he is a very practical man who understood the differences between different genres, so it's been a really fruitful collaboration for me.”

Doubtless for Pullman, too. And there's a huge audience waiting to find out exactly how fruitful.

The Golden Compass is released on December 7

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