Their 1981 wedding captivated the world, with millions of people enjoying what seemed like a real fairy tale.
From the outside, Princess Diana’s relationship with Prince Charles was a perfect match.
But by early 1982, a now pregnant Diana was so unhappy that she resorted to throwing herself down a staircase to get her husband’s attention during a visit to Sandringham, the late Queen Elizabeth’s Norfolk estate.
The Queen witnessed what happened and was left “trembling” and “absolutely horrified,” Diana later told royal biographer Andrew Morton.
In audio tapes sent to Morton for her biography, Diana, Her True Story, she claimed her husband fired her when she initially threatened to throw herself down the stairs.
Prince Charles and Princess Diana join the late Queen Elizabeth at the Braemar Games in Scotland in September 1981
Princess Diana attended a church service in Windsor on Christmas Day 1981
The prince and princess were staying at Sandringham House, pictured, when the incident occurred in 1982.
Charles accused her of raising the alarm and allegedly told her: “I’m not going to listen to you. You always do this to me. Now I’m going to get on.”
In response to Charles’s indifference and in an attempt to get his attention, Diana revealed to Mr Morton: “I threw myself down the stairs.”
She said she was trying to get Charles’ 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 witnessed the incident as it unfolded.
Diana said: ‘The Queen comes out absolutely horrified, shaking; she was so scared.’
The princess was four months pregnant with Prince William at the time, but explained: “I knew I wasn’t going to lose the baby, (although I had) quite a bit of bruising around my stomach.”
Prince Charles, Lady Diana Spencer and the Queen at Buckingham Palace in March 1981, four months before the royal wedding.
The couple, along with the Queen, wave from the balcony of Buckingham Palace on their wedding day in 1981
Diana and Charles standing outside St George’s Chapel on Christmas Day 1981
However, the incident did not provoke the reaction from Charles that Diana desperately wanted and she told Morton that “it was simply dismissal”.
When she returned from riding, the Princess claimed she “just carried on and walked out the door.”
Her response was influenced by advice from friends who felt Diana needed to “pull herself together,” wrote Robert Lacey in his book Battle of Brothers.
However, as Prince William’s due date approached, Charles spent more time with Diana and remained by her side when her first child 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 he was “very grateful to have been at Diana’s bedside all the time.”
The couple were staying at the late Queen Elizabeth’s Norfolk residence at the same time as the monarch and she witnessed the incident as it unfolded.
Princess Diana during a visit to Wales in October 1981
However, Princess Diana’s mental health problems continued later in life. When William was four, the princess collapsed during a trip to Canada.
She was battling bulimia at the time and told Charles she thought she was “on the verge of disappearing” before fainting during an exhibition at Expo ’86.
The princess received some help from doctors but continued to struggle and her marriage to Charles continued its downward spiral.
They eventually separated in 1992 before divorcing in 1996.
She told Mr Morton how Charles “told a lot of people that the reason the marriage was so unstable was because I was sick all the time”.
“They never questioned what he was doing to me.”
