For one night only the tables were turned on the X-Factor's judges as they risked ridicule themselves by donning tutus to join the cast of Billy Elliot at a charity gala performance.

Simon Cowell, Sharon Osbourne and Louis Walsh joined Sir Elton John, the show's composer, and Liam Mower, one of the most popular young actors to play Billy, to mark the sale of the millionth ticket.

Cowell, Osbourne and Walsh played examiners at the Royal Ballet School during a short scene last night at Victoria Palace Theatre.

Sir Elton told the Standard: "It was one of the funniest things I've ever seen when they made their appearance.

"But they were brilliant. Should they ever want to go back on stage again, they've got it made. Being in a tutu is a whole new career for Simon Cowell."

Cowell was characteristically arrogant on the subject of his stage debut: "There's already a rumour going around that we're up for a Tony Award. It was easy, but then we only had a couple of lines and we were not dancing with boxing gloves."

After the trio put on their tutus for an encore, Cowell joked: "Louis Walsh brought his own."

Osbourne was even more at ease, having appeared on stage in a regional tour of The Vagina Monologues. "I loved every minute of it," she said. "I wasn't nervous because I'm an exstage school brat."

However her husband-missed out. "Ozzy's just got back from Los Angeles and he's very jetlagged. But I think he was scared I would embarrass him," she added.

David Furnish, Sir Elton's partner and executive producer of Billy Elliot, said Mower, 14, who has left the cast to return to school in Hull, was back at Sir Elton's personal request.

Furnish said: "Because Elton was away in September for Liam's last performance he felt really sorry and wanted to plan a special farewell. So he roped in a few friends along the way."

The night raised £25,000 for The Place 2Be, which provides emotional and therapeutic support for vulnerable children. It is donating the money to schools in Easington, in the North-East, where the musical is set.