Prince Philip was furious after Prince Charles made this shocking confession.

Prince Charles’ biggest mistake in his life was not his decision to divorce Princess Diana. Many believed that it was when he made a shocking confession about his affair with Camilla Parker Bowles.

In a past interview with Jonathan Dimbleby, the heir apparent was asked if he was faithful and honorable to his wife, Princess Diana, during their marriage. Prince Charles said “yes” but when prompted by the interviewer “you were?” the Prince of Wales admitted that he was “until it became irretrievably broken down, us both having tried.”

Many understood it as Prince Charles’ confession about his affair with Camilla. According to Penny Junor in her book “The Firm,” Prince Philip was furious after learning Prince Charles’ confession and many shared the Duke of Edinburgh’s sentiments. In fact, they felt that what the future king did was the “worst mistake” of his life.

“Many regarded as the worst mistake of his life,” Junor wrote. “At the time many people thought it might cost him the throne.”

Following Prince Charles and Princess Diana’s split, the Queen and Duke of Edinburgh blamed their son more than their daughter-in-law. According to Robert Lacey, Prince Charles was blamed more because he was emotionally committed to another woman, Camilla, even before he married Princess Diana.

Although Prince Philip appeared to sympathize with Princess Diana, the Princess of Wales revealed that she wasn’t really happy with the Duke of Edinburgh’s advice to Prince Charles. According to the People’s Princess, Prince Charles’ father convinced him to marry her and reassured the future king that he could just get back with Camilla after five years if their marriage would not work.

“My father-in-law said to my husband, ‘If your marriage doesn’t work out, you can always go back to her after five years,’” Princess Diana revealed. “Which is exactly—I mean, for real I knew that it had happened after five—I knew something was happening before that but the fifth year I had confirmation.”

Prince Philip and Prince Charles
Prince Philip made Prince Charles nervous and neurotic after sending him to Gordonstoun. Pictured: Prince Philip and Prince Charles n to speeches before a statue of the Queen Elizabeth, The Queen Mother was unveiled on Oct. 27, 2016 in Poundbury, England. Getty Images/Justin Tallis