The new voice of Harry Potter

A London schoolboy has landed a last-minute role in the new Harry Potter film as the voice of the young wizard himself. As the first American review judges the movie not as good as the book, it has emerged that the main star Daniel Radcliffe, 12, had to be dubbed in two scenes when his voice broke before the end of filming.

Joe Sowerbutts, 13, from Putney, whose classmates say his voice sounds just like Daniel's, was drafted in by producers at Warner Bros. Joe provides Harry's voice in two scenes of the £90 million movie - one on a broomstick and one in a forest - as well as on Nintendo and PlayStation games. It is believed he will receive £200,000 for his efforts.

His mother Julie Sowerbutts is reported to have said: "It was a great honour for him but he's such a laid-back boy and has done so many other things it really wasn't that big a deal."

The first review of Harry Potter And The Philosopher's Stone describes the film, which will have its world premiere in London on Sunday, as "eye-popping", but not as good as the book. Time magazine, which was shown the film before the critics, says the movie was "not perfect" and the book "a more transporting piece of entertainment".

The American weekly said the makers sometimes assumed "a heavy load" in trying to bring all the novel's elements to the screen and what emerged was "essentially a greatest-hits compilation of the book".

It says Daniel Radcliffe is not as noisy as Harry Potter in the book, adding: "Some may wish he had been more rowdy". The child stars also often required "some patience on the part of viewers".

Daniel has signed a reported £1 million deal to star in the sequel, Harry Potter And The Chamber Of Secrets. By next summer, it will become clearer to the producers whether he will still resemble JK Rowling's creation enough to film the rest of the series.

Daniel's mother Marcia is a theatrical producer and his father Alan is a successful literary agent specialising in film and TV adaptations. Daniel expressed an interest in acting at five and by the time he was 10 had played the young David Copperfield in a BBC adaptation. It was, according to a friend, a normal, happy, life: "They are all rather lovely. I don't think it's an absolute coincidence that Daniel landed the part given his background. But he was never pushed the way some child actors are." The Radcliffes were at a play in the West End when Daniel was spotted by producer David Heyman.

Mr Heyman said: "I saw this boy who combined a wonderful sense of curiosity, openness and generosity with a warmth that wasn't sentimental or too cute.While I was staring at him, I heard my name, and next to him was a man I knew, Alan Radcliffe. He introduced me to his wife and son . The play was a blur - I kept looking behind me at Daniel. I called the next day and said, 'Alan, your son! Would you allow him to audition?'"

Comic Rik Mayall's role as the rude ghost Peeves has hit the cutting room floor. At 143 minutes, the film is still an hour longer than most children's films. Sources at Warner Bros say the cut was nothing to do with Mayall's performance.

Police are investigating the theft of props after they appeared for sale on the internet, it was reported today. A wizard's hat and three gold coins were taken from Leavesden studios, Hertfordshire.