By Caroline Westbrook
BBC News Online
As film fans prepare for the third Harry Potter film, BBC News Online asks whether its teenage stars are in danger of outgrowing their characters.
Watson, Radcliffe and Grint have grown up with their characters
Just as Harry Potter has grown up over the years, so has the actor who plays him in the films.
Daniel Radcliffe was just 10 when he was cast as the boy wizard. His co-stars Rupert Grint, who plays Ron Weasley, and Emma Watson, who stars as Hermione, were the same age.
But as Harry Potter and The Prisoner Of Azkaban is released, speculation has been mounting about how long the teenage cast can continue to stay with the series.
Radcliffe turns 15 in July, while Grint, the eldest of the trio, is almost 16. Watson recently celebrated her 14th birthday - not much older than their characters, who are hitting their early teens in the third book.
Fans of Radcliffe and his co-stars will be relieved to know all three have signed on for the fourth film, Harry Potter and the Goblet Of Fire, which is due for release in November 2005.
The trio as they were in 2001, when the first film was released
Some are concerned the actors are growing up faster than the books are being published and films being made.
"There will come a point when one, two or all three of them will move on," producer David Heyman recently told the New York Post.
"I don't know when that will be - with the fifth, sixth or seventh movies - but it's inevitable.
But other observers are more optimistic about the trio's futures at Hogwart's.
"Actors have been 'acting-up' in age and 'acting-down' for 100 years," says Colin Kennedy, editor of film magazine Empire.
"I don't think that the problems of additional make-up or forced perspective, to keep them all the same height, are as significant as finding a new Harry and introducing him to the established audience. "
"The way I see it, the older the characters get in the book, the easier they are to play them," adds Dan Jolin, Features Editor of Total Film.
"The actors are at that age where they can play slightly older rather than younger, and I think the producers would prefer to keep the same actors as they've become so recognisable."
"Whether they want to carry on playing the parts is another matter."
The film of the fifth book, Harry Potter And The Order Of The Phoenix, is due in 2007 - by which time Radcliffe will be 18.
But as the other two books in the series are still some way off publication, it could be years before the last two films are released.
Daniel Radcliffe will star in the fourth Potter film
That all suggests Radcliffe, Watson and Grint could be well into their 20s by the time Potter makes his final screen appearance.
If they were to remain in the roles, they would not be the first twentysomething actors to portray teenagers on screen.
Michael J Fox was 23 when he starred as 17-year-old Marty McFly in the 1985 blockbuster Back to the Future - and reprised the role in two sequels in 1989 and 1990, although the character was still in his teens.
Actress Stockard Channing was even older - 33, to be precise - when she took on the role of teenage wild child Rizzo in Grease, while co-star Olivia Newton-John, starring as 17-year-old Sandy, was 30.