The Lord Of The Rings, the film set to rival the hugely-successful Harry Potter phenomenon, has its world premiere on Monday. Film Writer Steve Pratt explores the fantasy genre.

THE pain was too much to bear. Actor Billy Boyd knew he could put off visiting the dentist no longer. But having toothache in the middle of the day on the security-shrouded New Zealand set of one of the year's most eagerly-awaited movies poses certain problems - especially if you're playing a hobbit.

So the patient arriving at the dental surgery was a strange sight, wrapped in a large green robe with the hood concealing his head and face, and wearing huge boots.

"There was great secrecy about the look of the hobbits, so I had to cover up," recalls the Glaswegian-born performer, who plays Pippin in The Lord Of The Rings trilogy. The boots concealed his outsize latex hobbit feet that took an hour a day to put on and another half-hour to remove. "I went to the dentist in the lunch break and, as I had dialogue in the afternoon, I couldn't have my face frozen by an injection. I told the dentist to give me a filling without anaesthetic. I sweated so much that my feet fell off," he says.

Boyd's pain was part of the agony and ecstasy in filming JRR Tolkien's The Lord Of The Rings, nearly 50 years after it was first published. Eighteen months and nearly $300m dollars were spent transferring the fantasy story from the page to the big screen. Three films have been made back-to-back, with the first, The Fellowship Of The Ring, having its world premiere in London on Monday before opening worldwide on December 19.

New Zealander Jackson, best known until now for low budget splatter movies like Bad Taste and the early Kate Winslet drama Heavenly Creatures, is well aware of the enormity of the project. Opening a month after another fantasy film involving wizards is the least of his worries. While others take bets on whether The Lord Of The Rings can beat record-breaking Harry Potter And The Philosopher's Stone at the box-office, Jackson is probably more concerned how fans of the books will respond to his treatment.

Bringing to cinematic life the Middle-Earth world of hobbits, elves, Gandalf the wizard, Sauron the Great, menacing Black Riders and the Orcs is a massive undertaking. And one of which its creator, pipe-smoking Oxford don Tolkien, would probably not have approved.

This is the man who had his number removed from the telephone directory because he was fed up with American students, under the influence of his books and probably pot as well, 'phoning him up in the middle of the night to discuss possible allegorical meanings of the plot.

The book was a sequel to his earlier novel The Hobbit. Total sales have passed the 100 million mark, although it was only a steady seller when first published in 1954. Tolkien himself thought it "too long and complicated and too slow in coming out". Only when the rebellious youth culture of the 1960s took up the cause of The Lord Of The Rings did it achieve cult status. It is, an observer noted, one of the greatest and unlikeliest success stories in literary history. What's more, its author is credited as being the godfather of fantasy as an entertainment genre, opening the way for everything from Star Wars to Harry Potter.

This isn't the first attempt to film the book. Director Ralph Bakshi made an animated version in 1978, but poor audience reaction meant a planned sequel was abandoned. Enter 40-year-old Jackson, a bearded figure in shorts and sandals who never went to film school but embarked on a film career making movies with his parents' Super 8 camera. Top independent Miramax bought the rights with the aim of getting him to make a two-part film. The budget soared and preparation stalled when the company asked him to compress it into one film. Jackson was adamant that too many characters and events would be lost.

"Anybody who read the book would have a natural disappointment," he says, mindful of his responsibility to the fans. Another independent, New Line, took over the project three years ago. The plan for three films was reinstated as Jackson prepared to transport movie-goers into the fantastical world of Middle-Earth. "I wanted to take all the great moments from the books and use modern technology to give audiences nights at the movies unlike anything they've experienced before."

Amazingly, Hollywood handed over vast sums of money to a relatively untried, non-American director to make not one, not two, but three films at once. The scale of the gamble was only too apparent. The isolation of New Zealand, a relatively unused location cinematically, gave Jackson the sense of what he calls "otherness" necessary for the story. The country also contained all the mountains, woods, marshes, rolling hills and sea needed to conjure up not just The Shire but everywhere else the hobbits journey. Authenticity was added by having Tolkien illustrator Alan Lee as the film's conceptual designer.

A cast of international names, including Ian McKellen, Cate Blanchett, Ian Holm and Christopher Lee, was recruited to feature alongside young actors such as American Elijah Wood (who plays the hero Frodo Baggins) and screen newcomer Billy Boyd. The production was planned like a military campaign with an army of experts, in everything from state-of-the-art computer-generated special effects to stone sculptors, recruited for this three Rings circus. This is a film where half the cast are only 4ft tall and some are 7ft tall. A range of tricks were used to achieve the little and large illusion.

Remarkably, little seems to have gone wrong given the epic scope of the undertaking. One leading actor left after a week, agreeing he wasn't right for the part, but was swiftly replaced without interrupting filming.

Throughout, the book was never forgotten. Jackson and the cast would constantly refer back to it. "Every time we shot a scene, I re-read that part of the book right before, as did the cast. It was always worth it, always inspiring," says Jackson. Initial reaction has been good. The first US reviews reckon The Lord Of The Rings is better than the Harry Potter movie. As for the fans, New Line set up the movie's website even before filming began in New Zealand to ensure they were kept informed every step of the way. "While you can never be totally faithful to a book, especially one over 1,000 pages, we have tried to incorporate the things that Tolkien cared about when he wrote the book, and make them the fabric of the films," says Jackson.

* The Lord Of The Rings (PG) opens on December 19.