LONDON, England (Reuters) -- Thousands of fans including pop star Madonna descended on central London on Sunday for the world premiere of "Harry Potter and the Goblet of Fire", the fourth installment of a hugely successful series of films.The darkest movie episode yet from J.K. Rowling's bestselling, seven-book series features young wizard Harry being tested to the limit in a magic tournament and meeting his nemesis Lord Voldemort in a dramatic climax.With death, danger and the first blossoming of teenage love at Hogwarts School of Witchcraft and Wizardry, the film has been ruled unsuitable for under-12s to watch unaccompanied by an adult, the first of the Potter films to get such a rating.Among the stars to grace the red carpet were American Madonna, German supermodel Claudia Schiffer and British actress Kate Beckinsale.The three teenagers who play central characters Harry, Hermione and Ron in the films also attended.Screaming girls waited hours in the rain for a glimpse of the actors, and especially Daniel Radcliffe, the 16-year-old who plays Harry. One banner among them read "Marry Me".Goblet cost an estimated $130 to $170 million, but it looks like a sound investment for studio Warner Brothers after the first three movies earned around $2.5 billion at the box office.British director Mike Newell said he wanted to recreate the atmosphere he remembered when at school."I remember being terrified of some teachers at school who were violent," he said in a recent interview. "The teachers would clout us. But I also remember things being absolutely hysterically funny, because there was such anarchy.""What I tried quite consciously to do was to make a movie which was entertaining for adults as much as it was for children. I knew there would be a lot of parents in there with nine-year-olds," he said.He also defended his decision to make Goblet a darker film than the previous three."There's a problem of credibility," he told Reuters in an interview last month to promote the film."If you think ... there is going to be the same sunlit, blush-toned childhood of film number one, there is a lot of questions that you will ask. You will tend not to believe that."He described the budget for the two-and-a-half hour Goblet as "colossal", although the film's backers still made him fight for money while making the film.The fifth Harry Potter film, "Harry Potter and the Order of the Phoenix", is due out in 2007.Copyright 2005 Reuters. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.