Simon Cowell sparked rumours that he popped the question to his girlfriend Mezhgan Hussainy after she was spotted with a huge sparkler on her engagement finger, The Sun reported today.

The Sun reported today the makeup artist was seen wearing the ring when the pair were photographed in the back of a car after a romantic Valentine’s Day meal.

Reports indicated the American Idol judge gave her the rock during the dinner they shared at celebrity haunt Mr Chow’s in London’s upmarket Kensington neighbourhood.

“He wanted to do something unexpected and out of character on Valentine’s Day and decided to splash out on a ring,” a source said.

Hussainy, 36, showed off the ring when she placed her hand over Simon’s as they made their way back to his London mansion after their meal.

Cowell, 50, previously declared he would never wed and broke up with long-term girlfriend Terri Seymour in 2008 because he did not want to get married.

The TV mogul denied getting engaged to Afghan-born Hussainy.