Prince Charles and Princess Diana struggled very early on in their marriage but their fans weren’t aware of their issues.

In the documentary “Inside the Crown: Secrets of the Royals,” royal photographer Ken Lennox revealed the moment where he noticed cracks in the royal couple’s relationship.

While on a tour of Australia, the Prince and Princess of Wales visited the Sydney Opera House. Lennox took photos of Prince Charles and Princess Diana during their engagement and he saw the late royal crying hysterically.

“I’m about four feet from the Princess, and I’m trying to get a bit of the opera house in the background and some of the crowd, and Diana burst into tears and wept for a couple of minutes.  After it was over, I went to see the press officer for Prince and Princess, and I said, ‘What happened?’” Lennox said.

Prince Charles and Princess Diana’s press officer told Lennox that the latter cried because of the heat and her jet lag. Lennox said that he just accepted what the press officer told him.

The royal photographer also said that Prince Charles didn’t seem to notice that Princess Diana was crying at that time. And if he did, it was evident that he looked away.

According to Lennox, that moment showed the first sign that something was wrong in the royal couple’s marriage. And it didn’t take very long for the public to see that there were also other things going on behind closed doors.

For instance, Princess Diana was aware that her husband was having an affair with Camilla Parker Bowles. According to royal author Andrew Morton, the Princess of Wales saw a bracelet inside Prince Charles’ office and was told that it’s a gift for Camilla Parker Bowles.

Even though Princess Diana knew about Prince Charles and Camilla’s affair, she still chose to stay married to her husband. It was only after her interview with Martin Bashir for Panorama that the Queen asked the royal couple to file for divorce.

In 1996, Prince Charles and Princess Diana announced that they were splitting. At that time, their sons, Prince William and Prince Harry stayed with Prince Charles at Buckingham Palace.

Less than a year after the royal couple’s divorce, Princess Diana passed away following a tragic car accident. She was with her boyfriend, Dodi Al-Fayed, who also died in a car accident.