The X Factor semi-finalists have performed a secret gig for competition winners.

Where was this secret gig? The Royal Albert Hall, Earls Court? No it was in the basement of a Carphone Warehouse shop in London's Oxford Street.

Alexandra Burke, Diana Vickers, Eoghan Quigg and boy band JLS performed a selection of songs from the show so far to 28 competition winners.

With all 28 fans cheering her on in a mobile phone shop's basement, Diana, 17, sang Blondie's Call Me, which she sang in the disco scenes show, and Man in the Mirror from the Michael Jackson show.

Alexandra, 20, had a bad throat so sang only one song. Asked her reaction to news she was the bookies' favourite to win, she said: "It's very, very scary. I got that news yesterday. It actually shocked me as I wasn't expecting that."

Alexandra also defended Britney Spears, who has been criticised for miming during her guest performance on last Saturday's show. "She put on a really good show. She looked amazing too."

JLS sang two songs, with Marvin Humes, 23, and Ortise Williams, 21, taking the lead because front-man Aston Merrygold, 20, has lost his voice.

During their Stand By Me medley Aston pulled two fans on to the stage to be serenaded. "It was like a dream come true. Everyone vote for them, they are amazing," said Megan Hart, 14, from London.

Eoghan, 16 denied rumours he was seeing fellow contestant Diana. "We're really good friends. Ruth and Alex were good friends, and JLS have got each other. She's not my type anyway!"

The four acts will take part in the semi-finals this Saturday.

The show's winner will release a version of Leonard Cohen's Hallelujah before Christmas.