Prince William reportedly had a thing for socialite and actress Isabella Calthorpe ever since they met in 2004 and is said to have pursued that when he split with Kate in 2007.
Calthorpe is the daughter of banking heiress Lady Mary Gaye Curzon, and the half-sister of Prince Harry's ex-girlfriend Cressida Bonas.
It's been previously reported that Kate got so jealous of William and Isabella's budding friendship that she 'stormed out of a ball when he spent the night talking to her.'
According to royal author Katie Nicholl, who wrote William and Harry: Behind the Palace Walls, Isabella is the reason behind Kate and Williams 2007 breakup.
'He had fallen for her in a huge way and wanted to be with her', Nicholls told the Daily Mail.
'He propositioned her several times that summer and although Isabella was single, she knocked William back and said it would be too damaging for her and her career.'
'She is a name in her own right and on her way to becoming hugely successful. In her view, being affiliated with William in a girlfriend capacity would be damaging for her.'
Isabella was a guest at William and Kate's wedding and is now married to Sir Richard Branson’s son, Sam Branson.