Simon Cowell’s London home was ransacked while the “American Idol” judge was in the United States.

The American Idol judge is devastated after thieves raided the Holland Park pad, making off with jewellery, silver, and electrical equipment.

Cowell has been branded “unwise” by police after he left his house keys with building constructors who were refurbishing his $11.7 million house.

“It was an unwise decision to say the least. You wouldn’t believe some of the things Mr Cowell had accumulated over the years that the thieves took a fancy to,” London investigators say.

“What has happened in similar cases is that someone copied the main key. I’m sure the builders would have been very careful about who had access, but it’s not always easy when a number of sub-contractors are coming in and out of the place,” a mole tells the British tabs.