Sir Paul McCartney's estranged wife Heather Mills is facing fresh criticism after reportedly having an affair with her fitness coach. The former model formed a strong bond with personal trainer BEN AMIGONI, who has split from his long-term partner as a result. The pair are currently spending time in the US together, but dumped girlfriend JOANNE BRADFORD is still stunned by the unexpected break-up. She tells British newspaper The News Of the World, "One minute we were really happy together and the next we're apart. "I've spoken with Ben and he insisted he and Heather are just friends." Bradford's father BERNARD adds, "It was when Paul and Heather split the problems started. I think Ben's just been swept up in it all because Heather's a star."