Junior wizards will be banned from the latest Harry Potter film unless accompanied by an adult after the movie today became the first in the franchise to receive a 12A rating.

Harry Potter and the Goblet of Fire, the fourth film in the blockbuster series, was deemed by censors to be "too intense" to carry the PG classification of previous instalments.

Warner, which produces the films, had expected the stricter rating after a guidance screening to the British Board of Film Classification earlier this year.

The company has not yet said whether it intends to appeal against the rating, which effectively rules that the film is unsuitable for a large proportion of its target market.

Last year's instalment, Harry Potter and the Prisoner of Azkaban was considered to be a determinedly darker and more sophisticated yarn, yet took £46 million at the British box office, second only to Shrek 2.

The next episode, which features the chilling rebirth of Lord Voldemort and his evil Death Eaters against the backdrop of a tense Wizarding tournament, is reportedly edgier still.

Helen Pang, of the BBFC, said: "The film is much darker and scarier than the previous three, which were all classified PG.

"You can really spot the differences in the four films. The first one, Harry Potter and the Philosopher's Stone, was classified back in October 2001 and Harry and his friends were so sweet and innocent then.

"As the characters have become teenagers and are more experienced in magic, the tone of the films has become darker, the moments of intensity more frequent and there are far fewer jokes and lighter moments.

"The result is that this is the first Harry Potter film at 12A. Be prepared for a very different film to the first three," she told the BBC.

The film - whose tagline is 'Difficult Times Lie Ahead' - features performances from Eric Sykes and Timothy Spall, as well as the regular cast of Daniel Radcliffe as Harry Potter, and Emma Watson and Rupert Grint as his friends Hermione and Ron.

Mike Newell, the first British director in the series, has turned JK Rowling's 734-page novel into a film that clocks in at 157 minutes. The studio originally had planned to split the book in half, releasing the second episode after a six-month interval.

The decision to award the film a 12A rating was welcomed by teenage fans contributing to Potter websites.

Ellie, 14, from Devon, wrote: "When I went to see the first film there was a tiny little kid behind me who was terrified. I think the new rating is probably good."

Matt, 13, from Conwy, added: "I think the books get more scary and so the films should too."

The film, released in the UK on 18 November, has been given a PG-13 rating in the US.

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