Royal expert, Katie Nicholl mentioned Isabella in her 2010 book William and Harry: Behind the Palace Walls, and suggested her connection to William prompted Will and Kate's trial separation in 2004.
"He had fallen for her in a huge way and wanted to be with her. 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," a royal insider told the Daily Mail in 2007.
"It was obviously the break that William needed, and by Christmas they were back together again, although Kate had a condition. Word had reached her of William's visits to Isabella, and Kate insisted that William was not to contact her again."
While these comments are likely nothing more than tabloid 'hearsay', it certainly makes the royal family dynamic sound like an action-packed season of The Crown.