Here's what it says on his fansite:
After spending Christmas in Sheepscombe with his family, he'll be jetting off to Italy to shoot a film in Rome for two-and-a-half months which is based around the signing of the Magna Carta.
"There are some really interesting and good actors in it – Richard Attenborough, Bob Hoskins and Robert Carlisle," William says.
"I'm going to be playing, this sounds ridiculous, but someone who can read and write as most of the people during the time of the Magna Carta couldn't.
"I'm lucky to be going from children's media into an adult film and make that transition. It's one of those things you always hope is going to happen but are never entirely sure.
"I'm hoping that will go ahead but you never know with these film companies."