The time the Queen saw Princess Diana throw herself down the stairs

Their 1981 wedding captivated the world, with millions delighting in what appeared to be a royal fairy tale.

From the outside, Princess Diana's relationship with Prince Charles was a match made in heaven.

But, by early 1982, now-pregnant Diana was so unhappy that she resorted to throwing herself down the stairs to get her husband's attention during a visit to Sandringham, the late Queen Elizabeth's estate in Norfolk.

The Queen witnessed the aftermath and was left 'shaking' and 'absolutely horrified', Diana later told royal biographer Andrew Morton. 

In audio tapes sent to Morton for his biography, Diana, Her True Story, she claimed she was dismissed by her husband when she initially threatened to throw herself down the stairs. 

Accusing her of crying wolf, Charles allegedly told her: 'I'm not going to listen. You're always doing this to me. I'm going riding now.'

In response to Charles's disregard and in a bid to get his attention, Diana revealed to Mr Morton: 'I threw myself down the stairs.'

She said she was trying to get Charles's attention and wanted him to listen to her.  

The couple were staying at Queen Elizabeth's Norfolk residence at the same time as the monarch and she happened to witness the incident as it played out. 

Diana said: 'The Queen comes out, absolutely horrified, shaking - she was so frightened.'

The Princess was four months pregnant with Prince William at the time but explained: 'I knew I wasn't going to lose the baby, [though I was] quite bruised around the stomach.'

However, the incident didn't spark the reaction from Charles that Diana desperately desired and she told Mr Morton how 'it was just dismissal'. 

When he came back from riding, the Princess claimed he 'just carried on out of the door'. 

His response was influenced by advice from his friends who felt Diana needed to 'pull herself together', Robert Lacey wrote in his book, Battle of Brothers. 

However, as Prince William's due date approached, Charles did spend more time with Diana and stayed by her side when their first son was born. 

In doing so, he became the first male royal to be present at a birth.  

In a letter to his godmother, Patricia Knatchbull, Charles said how he was 'so thankful I was beside Diana's bedside the whole time'. 

However, Princess Diana's struggles with her mental health continued later on. When William was four years old, the princess fainted during a trip to Canada.

She was battling bulimia at the time and told Charles she thought she was 'about to disappear' before passing out during an exhibition at Expo'86.

The Princess received some help from doctors but continued to struggle and her marriage to Charles continued a downward spiral. 

They eventually separated in 1992 before divorcing in 1996.

She said to Mr Morton how Charles 'told a lot of people the reason why the marriage was so wobbly was because I was being sick the whole time. 

'They never questioned what it was doing to me.'