TV music mogul Simon Cowell was treated to a surprise 50th birthday party this weekend - three months before he is due to celebrate the milestone age.

The American Idol judge arrived at what he thought was a bash to mark his ex-girlfriend Jackie St Claire's birthday at a venue in London on Saturday night.

However, Cowell was shocked to discover all his friends waiting to surprise him with an early celebration of his 50th - brought forward because he will be too busy filming British TV talent show X Factor to celebrate properly in October.

The star was joined by his fellow American Idol judge Randy Jackson, as well as his X Factor colleagues Dannii Minogue and Louis Walsh - who all joined forces to serenade the birthday boy with a rendition of Carly Simon hit You're So Vain. Cowell's Britain's Got Talent co-star Piers Morgan also attended the event, which was organized by St Claire.

A source tells Britain's Daily Mirror newspaper, "Jackie went to extraordinary lengths to organize the bash for Simon. She even told the guys performing they were singing for her - but it turned out they were there for Simon. She knew the performance would really make him laugh. Dannii took the lead vocals and the others came out providing the comedy for the show. Jackie knew Simon would find it hysterically funny especially when Louis joined in the singing. Simon is so vain but, unlike some, he is the first to admit it. So it was the perfect joke."

While Cowell himself adds, "It was a fun night. I went on my own, well with my mum, and had no say over the guest list. But it was all fine."

The TV mogul will turn 50 on October 7th.

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(This news article provided by World Entertainment News Network)