On September 17, Kate Middleton held her first official meeting in the Windsor Castle offices she shares with Prince William following the end of her cancer treatments. This week, the princess tapped a special guest to join her in the office as a palace coworker for the day.

James Middleton shares in his new book, "Meet Ella," how his sister, Catherine, Princess of Wales, told him and sister Pippa she was engaged to Prince William.

Their Wednesday's joint royal engagement follows Kate's statement last month, in which she announced that she had completed her chemotherapy treatment.