Simon Cowell says finding a fan hiding in his house with a brick was like "something from a horror movie".

The music mogul was watching his appearance on a TV talk show on Saturday night when he heard a noise. Police rushed to his exclusive London home after he found a woman armed with a brick hiding in his bathroom.

Simon's spokesperson Max Clifford says the popular TV personality was shaken up by the incident.

"There was a loud bang and Simon rushed upstairs to find out what was going on. It came from the bathroom so he went in and there was a woman standing there holding a brick. She had smashed her way in through the window and it was unclear how long she had been there or what she was doing," he told British newspaper The Sun.

"It was a very frightening experience for Simon, who told me it was like something from a horror movie. He was just very lucky that all she had was a brick. She could have had a knife, a gun or any other weapon."

The 52-year-old's on-site security team arrived to detain the 29-year-old woman before police came to arrest her. She was taken to a police station and is believed to have been examined by a psychiatrist.

According to the publication, she has been charged with aggravated burglary and is due to appear at West London Magistrates' Court today.

Simon is not believed to know the woman, and is now ramping up security at his west London home.

A source says the TV star has been naturally shaken up by the incident.

"Simon is one of the biggest stars in the world but he is very much a people person and doesn't walk around surrounded by big, burly bodyguards. He makes a point of shaking hands and speaking to people when he's going about his business. This is bound to make him more wary about being so open with strangers," the insider revealed.