The Sun revealed today that Gary has enlisted the help of Cheryl for judge's houses but managed to keep it a secret from the show's bosses- including Simon Cowell.
A source from the show told the Sun: "Only Gary's intimate inner circle know. He hasn't even discussed it with Simon or ITV bosses. It's seriously top secret stuff."
We wonder what Simon's face looked like when he found out? Priceless, no doubt.
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The source continued: "They're all under the impression that it's going to be Robbie [Williams]."
"No one even noticed that the dates of recording clashed with Robbie's new solo tour."
This is sounding increasingly like an undercover M15 operation than a celebrity booking if you ask us!
Gary hatched the plan with Cheryl over a drink after they performed together at the Queen's Diamond Jubilee concert.
The source added that Cheryl was more than happy to join Gary saying: "She loved the mischief of it."
We bet she did, pulling a fast one over Simon Cowell sounds right up Cheryl's street.
Last year, Cheryl was unceremoniously dropped from the US version of the show after spending less than a week on the panel.