Diana cried as Prince Charles left for Australia, but it wasn't because she'd miss him.

On March 29, 1981, pictures of Princess Diana dressed in a red coat, crying at the airport as her then fiance Prince Charles departed for a five week trip to Australia, emerged in the media.

The vulnerable moment was believed to indicate her sadness for Charles leaving for so long, but in hindsight it marked the emotional end of the pair’s tumultuous relationship, in which Diana eventually experienced severe depression.

Now I watching a film of princess Diana ???????? , she’s getting a lot of oppression from her husband and Camila and even the Queen ???????????? when she crying at Airport ???? I felt so badly .???? because Camila asked to get a lunch with her,, and Blessed her in her marriage..???????????? pic.twitter.com/yRwzhnnFmd

— ???????? (@Julianna_Luj) April 23, 2018

According to a National Geographic documentary Diana: In Her Own Words Princess Diana was crying at the airport because of Camilla Parker-Bowles.

“That was nothing to do with him going,” she said in the documentary.

“The most awful thing had happened before he went… I was in his study talking to him about his trip. The telephone rang. It was Camilla. Just before he was going for five weeks. And it just broke my heart, that.”

This was just the beginning of Diana’s heartbreaking struggle with her marriage, post-natal depression and her husband’s affair with Camilla Parker-Bowles.

After weeks of hints – like her soon-to-be husband spending time at the Parker-Bowles country home “quite a lot” and Camilla’s seemingly intimate knowledge of their plans – Diana learned the truth when she happened upon a bracelet Charles had designed for his mistress. She added that when she confronted her fiancé about it, it was clear he didn’t care.

Diana said at that moment she seriously considered breaking off her engagement, but her sisters talked her out of it.

“I went upstairs, had lunch with my sisters who were there. And I said ‘I can’t marry him, I can’t do this, this is absolutely unbelievable.”

“And they were wonderful and said, “Well, bad luck, your face is on the tea towel, so you are too late to chicken out’.”

But of course, the then Lady Diana Spencer did decide to follow through with her wedding, and married the Prince of Wales at St Paul’s Cathedral on July 29 1981.

By 1996, after welcoming sons Prince William and Prince Harry, the couple’s divorce was finalised. Almost a year later to the day, on August 31 1997, Diana was killed in a car accident in Paris.

You can watch ‘Diana: In Her Own Words’ on Netflix.