The story of King Arthur and the Grail did not end with his death: research reveals that, through Princess Diana, Prince William Arthur Windsor is descended from Arthur and could be the “Once and future king.” In this extraordinary book, Adrian G. Gilbert reveals the location of many sites central to the Arthurian legend and crucial core teachings of Christianity that were kept secret—until the day a new Arthur, one with the holy blood of the family of Mary, would once again sit upon the British throne.