Diana, Princess of Wales and King Charles III once held “deep affection” for one another, the iconic late royal’s lost letters revealed. “There was a period of great love between them,” veteran royal biographerIngrid Seward told an outlet. The princess was reported to have said that she wanted the world to know about the love letters then-Prince Charles used to send her in the earliest years of their union, which ended in divorce in 1996. “Diana told me very shortly before she died that she wished people could see the love letters that she had from Charles,” Seward added. “She really wanted pe…