Simon Cowell reportedly split from fiancee Mezhgan Hussainy last month.
The music mogul - who recently said he was "not sure" if he was still engaged to the make-up artist - is said to have called time on their relationship a few weeks ago although the break-up was amicable.
A source told The Mail on Sunday newspaper: "Simon and Mezhgan split up in August. He called it off and she wasn't that surprised or even very bothered about it. Mezhgan told her friends she knew it had been coming for a while. She offered him the ring back but he has insisted she keep it.
"As with all his exes, he is being very generous, but he is already dating again and he has been on a dinner date or two with a mystery British brunette."
Mezhgan - who put on a united front with Simon at the premiere of the US version of 'The X Factor' last week - is now living in Simon's $5m Beverly Hills home after moving out of the house they once shared.
The property is dubbed his "girlfriend graveyard" by friends because it is where his former lover Terri Seymour went after the pair separated in 2008.
Sources claim one of the reasons the couple - who got engaged last February after a whirlwind romance - split was because Mezhgan didn't get on that well with Simon's beloved mother Julie.
One said: "Simon knew it wasn't going to end in marriage. There were commitment issues on his part and the added problem that Mezhgan didn't get on all that well with Simon's mother Julie.
"The pair would often argue about how Mezhgan spoke to him."