Prince Harry claims his brother, Prince William, “felt tremendous guilt” for not speaking up about his father’s affair with Camilla Parker Bowles. The Duke of Sussex writes in his explosive memoir, “Spare,” that his mother Princess Diana’s “maths was off” when she famously told Martin Bashir in 1995 that there were “three people in this marriage.” “She left Willy and me out of the equation,” the 38-year-old writes in the book, which hits US shelves on Jan. 10. “We didn’t understand what was going on with her and Pa, certainly, but we intuited enough, we sensed the presence of the...