Lady Diana Spencer was only 20 years old when she married Prince Charles and became the United Kingdom’s own Princess of Wales. To the 750 million viewers who watched her 1981 wedding on television, Diana was a charming, down-to-earth princess who’d won her fairy tale marriage. But a decade later she sadly described the wedding as “the worst day of my life.”

Princess Di, as she was affectionately known, made that confession during a series of taped interviews with journalist Andrew Morton, who was writing a book about her life. She spoke candidly about her troubled marriage, her struggle with bulimia, and her difficulty handling life in the public eye. Most of the material has never been broadcast, but viewers