Prince William's American Ex-Girlfriend?

Prince William's American Ex-Girlfriend?

A new book has the details of the day Prince William broke up with Kate Middleton, and his relationship with a beautiful American heiress.

Respected biographer Christopher Andersen reveals that William actually called off the relationship by cell phone, telling Kate, "It just isn't going to work."

The book, William and Kate: A Royal Love Story, details the prince's relationship with American heiress Anna Sloan, who met William while they were both students in Scotland.

When William visited Anna in Nashville in 2004, Kate was said to be "deeply hurt."

He and Kate later got back together, and the rest is history.

The happy couple is featured in a new documentary called William and Kate: Modern Monarchy, which will air on BBC America.

Prince William and Kate are set to walk down the aisle on April 29, 2011.