Prince William had a panic button installed in Kate Middleton’s apartment when they dated, book claims

Kate Middleton became the Duchess of Cambridge when she married Prince William in 2011.

The bestselling author previously wrote a biography on the Princess of Wales titled "The Diana Chronicles," which was published in 2007. For her latest book, Brown said she spoke to more than 120 sources who were close to senior members of the royal family.

The Duke and Duchess of Cambridge met in 2001 as students at the University of St Andrews in Scotland. William told The Telegraph they were friends for over a year before a relationship blossomed. While the tabloids reported that the couple called it quits in 2007, they had reportedly gotten back together later that year.