Princess Diana, Prince Harry, Prince William and Prince Charles
Prince William was mortified when he learned about Princess Diana’s tell-all interview after Prince Charles divorce. Pictured: Princess Diana, Prince Harry, Prince William and Prince Charles watch the parade march past as part of the commemorations of VJ Day on Aug. 19, 1995 in London. Getty Images/Johnny Eggitt

Prince William was reportedly humiliated when he learned about Princess Diana’s secret interview.

The Duke of Cambridge was only 13 years old and was away at boarding school when he learned about his mom Princess Diana’s tell-all interview. Prince William reportedly didn’t approve of it and was shocked by the big revelations she made during the interview.

“He was mortified when Princess Diana gave a now-infamous interview to the BBC's Panorama, during which she lifted the lid on her marriage and revealed her husband's affair with his long-term mistress, Camilla Parker Bowles, who was married to Andrew Parker Bowles at the time,” Katie Nicoll wrote in her book, “Kate: The Future Queen.”

“To William's horror, she also spoke candidly about her affair with former Life Guards officer James Hewitt, a family friend who had taught William and Harry to horse ride,” Nicholl added.

Prince William was reportedly embarrassed and distressed over living through his parents' divorce with the press surrounding it. The school made its best effort to protect the future king, but many of his peers still watched the program.

For weeks, paparazzi lurked in the shadows of Windsor Castle waiting for a chance to grab a shot of Prince William, who usually headed there during the weekends to be with his grandparents, Queen Elizabeth II and Prince Philip. It was a difficult time for Prince Charles and Princess Diana’s eldest son.

The Queen Mother was reportedly also “deeply shocked” and detested Princess Diana when she learned about her interview. Queen Elizabeth II’s mother couldn’t comprehend the need to share one’s troubled marriage with a biographer.

“It is always a mistake to talk about your marriage,” Queen Mother told Sir Eric Anderson, the former Provost of Eton College in their 20-hour interview, in response to Princess Diana’s shocking tell-all.

Although there were times when Princess Diana embarrassed Prince William, there were also moments when she had second thoughts about her decisions because she didn’t want her son to be humiliated.

According to Beth Halle, a journalist for Daily Mail, Princess Diana had doubts about wearing her popular blue navy gown with stylish lace trim when she partied with the fashion elite at the Met Gala in New York in 1996. Prince Charles’ ex-wife reportedly feared that her teenage son would find the Dior gown racy and be embarrassed by her. Apparently, things turned out well and wearing the gown became one of Princess Diana’s key moments in fashion history.