Simon Cowell has said he feared for the safety of his baby son Eric when a burglar broke into his home.
The music mogul's mansion in Holland Park, west London, was entered in the early hours of Friday morning, with an intruder taking cash and jewellery.
Cowell told The Sun newspaper that he and partner Lauren Silverman ran to check on the 21-month-old child after a bodyguard woke them to tell them about the break-in.
He said: "That was the first thing we did, to make sure he was OK. Apart from the fact someone broke into my house and stole my stuff, which is scary, it could have been worse. Thankfully no one was hurt."
A security guard who was sitting in a car nearby drove after a suspicious-looking person he saw in the street.
M'Bathonha Mendes told the Sunday Mirror: "The adrenaline just kicked in. He was trying to get something out of the bag and I ran up to him, put my hand on his shoulder and said, 'Wait a second'.
"He jumped and then dropped the bag and ran."
He said that the bag "felt like there was a lot of jewellery in it".
The newspaper quoted a security source saying the contents of the bag were worth £500,000.
The Metropolitan Police said officers were called to an address in W14 at around 2.20am to reports of a burglary in progress, but the suspects had left the area.
Cowell mentioned the burglary on Saturday night's X Factor, joking that Reggie 'N' Bollie's song Locked Away was "very appropriate".
He referred to the incident after the first act performed on the semi-final of the ITV show.
Reggie 'N' Bollie, who are mentored by Cheryl Fernandez Versini, sang Locked Away by R City featuring Adam Levine.
When he was asked what he thought of their performance, Cowell said: "What was that about?"
He then joked: "Very appropriate the night after I get burgled."
Meanwhile, Cowell does not have any acts left in this year's competition, which will come to a close with next weekend's grand final.
Rita Ora's two girls Lauren Murray and Louisa Johnson, Nick Grimshaw's boy Che Chesterman and the one remaining group Reggie 'N' Bollie all want to make it to the end but one act will be eliminated tonight.
While Cowell was left unimpressed after Reggie'N' Bollie's first performance, he loved their mash-up of I Gotta Feeling/I Like To Move It.
"The final would not be the final without you two in it," he said.
Johnson got a standing ovation from all four judges for her rendition of It's A Man's World, with Fernandez Versini hailing her as "absolutely fantastic" and Cowell saying she had delivered a "masterclass".
He added: "I know it's a different show but Britain has got talent."
Murray impressed the panel with her version of Runnin' (Lose It All), with Cowell hailing it as a "great performance" and Ora telling her: "You can obviously sell records."
Chesterman had Grimshaw and Fernandez Versini in tears after his performance of Amy Winehouse's Love Is A Losing Game.
The former Girls Aloud star said it "really struck a chord" with her, adding: "Amy would have loved that rendition."
Grimshaw said it was "really spectacular", while Cowell said it was good "but a bit ordinary".
Bookies say Johnson is the shortest price any X Factor contestant has been to win the show heading into the final.
She is 1-4 to win ahead of Reggie 'N' Bollie who are 8-1 second favourite, Chesterman can be backed at 9-1, while Murray is 14-1 to win the show, Coral said.