Charles Spencer's Diana book rattles Buckingham Palace, experts say

King Charles III and Prince William are said to be furious at Charles Spencer's new book, which makes damning allegations about the monarch and reopens decades-old wounds within the royal family. The claim was made by several royal experts who spoke to Fox News Digital after "Swan Song: Diana, My Sister" was published on Tuesday. In it, Princess Diana's brother says he argued with then-Prince Charles over palace plans to have William and Prince Harry, then 15 and 12, walk behind their mother's coffin during her 1997 funeral procession. Most notably, Spencer alleged that after Diana died at age 36 in a car crash, Charles "sounded giddily elated — like a lottery winner." He wrote that Charles "went ballistic" during an argument they had over William and Harry. Spencer said Charles then hissed, "Rest assured, we'll forget her soon enough."