Gareth Gates: Beat Will Young in poster sales

The other eight finalists were also on the billl on the first date of the 21-date tour that will also see them perform in front of the Prince of Wales.

Gates, whose debut single Unchained Melody is expected to top the charts when it is released on Monday, proved more popular than his rival Young, who recently revealed he was gay - at least going by how much merchandise was sold.

"We sold slightly more Gareth badges than Will ones," a sales assistant at the venue said.

"And when it comes to the posters, we've just sold loads more - the girls obviously are far keener to have him on their walls."

Gates performed his new single before playing the piano in a duet with 16-year-old Zoe Birkett.

Young started with a version of The Doors' classic Light My Fire before singing one of the tunes on his record-breaking single, Evergreen.

Aaron Bayley got a good reception from the crowd

The single, a double A-side with Anything Is Possible, was the fastest-selling single in UK chart history and has sold more than 1.5 million copies so far.

His performance followed an appearance at the Top of the Pops studio after a row between the TV show's producers and his record company meant he did not perform on last week's programme.

The Pop Idol stars will do it all again on Friday night - and the 18,000 tickets for the first two Wembley Arena shows had been snapped up by fans in two-and-a-half hours when they first went on sale.

Thursday's concert was hosted by Pop Idol judge Nicki Chapman, and the show was opened by a rendition of Wham!'s Freedom by Korben, who was the first singer to be voted off the TV show.

Jessica Garlick will also sing at the Eurovision Song Contest

Darius Danesh received one of the best receptions of the night when he sang It's Not Unusual, made famous by Tom Jones.

Before that, Aaron Bayley and Birkett had won big cheers.

Each performer has been reported to be earning �100,000 each from the tour.

The show also featured the other finalists, Jessica Garlick, Laura Doherty, Rosie Ribbons and Hayley Evetts - but Rik Waller is not on the tour because he pulled out of the Pop Idol final.

Prince Charles is due to join fans at one of the concerts, on 6 April, which is expected to raise �250,000 for his charity, the Prince's Trust.