Harry Potter producer David Heyman has revealed that he is "optimistic" that the film's three main stars, Daniel Radcliffe, Rupert Grint and Emma Watson, will return for the fifth film in the series.

At the DVD launch of Harry Potter and the Prisoner of Azkaban, Heyman said, "The kids are on for the fourth. We now will start discussing the fifth, it's the same on each film.

"You're in the middle of the third you discuss the fourth, you're in the middle of the second, you discuss the third.

"I hope they stay with us and they'll stay with us as long as they want to. There may come a point some day where they decide not to and if they do, they'll go with all of our blessings.

"But I hope they stay and they're wonderful, and I'm cautiously optimistic that we'll have them again for five."