A new biography set for release this week argues that Princess Diana had a greater lasting impact on the British royal family than either Kate Middleton or Meghan Markle, the two women who followed her into marriages with future kings of England. The book, "The Four Wives of Windsor," by biographer Simon Vigar, examines the influence of four women who married into the royal family: Diana, Queen Camilla, Middleton and Markle. "She made the royal family more relatable and more touchy-feely," Vigar said. Vigar said the full extent of Diana's influence on the institution was not always understood by those working within the royal household at the time. He cited an unnamed source who had worked at Kensington Palace as saying the royal family struggled to fully grasp the scale of Diana's impact while she was alive.