How would you like to go behind the scenes on the set of the next Harry Potter film? What about meeting the stars of the films? And best of all actually appearing in Harry Potter and the Deathly Hallows itself?

It may sound too good to be true, but one fortunate person will have the chance to do all of these things if they win an incredible competition taking place in the UK at the moment.

However, winning the competition will require a great deal of luck.

Last Friday, two young stars from the Harry Potter films released 1,000 black balloons from the Millennium Bridge in London (fans of the films will remember that bridge from the explosive opening scene of Harry Potter and the Half-Blood Prince).

Cast members released the balloons on a London bridge

Each balloon has a ticket attached that entitles the holder to enter aprize draw. The winner of the draw will visit the set of the next film and take a small role as a moving portrait on the walls of Hogwarts School.

So all you have to do is find one of the balloons, enter the draw, win it, and Bob’s your uncle.

Matthew Lewis, who plays student wizard Neville Longbottom said: "The winner will be able to see all the stuff behind the scenes."

"People always assume the bigger sets are all computer-generated, but a lot of them are actually there," he continued.

Evanna Lynch, who plays Harry’s friend Luna Lovegood, told the BBC that filming on the Deathly Hallows, which will be released in two parts, was "about half-way through".

And even though the film is the last in the series, the "atmosphere is electric – everybody is having such a great time" said Ms Lynch.

So if you want to be part of the fun, keep your eyes peeled for a black balloon.

Who knows? With a little of Harry’s magic, one might make it all the way to China.