The Queen wrote a letter to Princess Diana just weeks after she gave a tell-all interview on the breakdown of her marriage to BBC Panorama.
In the interview, which was watched by 22.8 million people, Diana famously told interviewer Martin Bashir there were "three of us" in her marriage to Prince Charles - referencing his love for Camilla.
As well as stating the monarchy was in desperate need of modernisation, Diana described the prince's camp as the "enemy".
With the public taking Diana's side following the astounding interview, she caused major embarrassment for the royals and threw them into crisis.
After this the Queen decided to write a letter to Diana, ending her marriage to Prince Charles, the Mirror reports.
The Queen wrote: “I have consulted with the Archbishop of Canterbury and with the prime minister and, of course, with Charles, and we have decided that the best course for you is divorce."
Even though the couple had already been separated for three years, they hadn't technically divorced as Diana felt she needed "clarity on a situation that has been of enormous discussion".
The Queen's demand for divorce reportedly left Diana furious as it is thought she told her butler Paul Burrell: "That’s rich! They get to decide whether I divorce!"
But just days later, Buckingham Palace formally announced the divorce in a statement saying "after considering the present situation the Queen… gave them their view, supported by the Duke of Edinburgh, that an early divorce is desirable".
The following year on August 28, 1996, the divorce was complete and the couple's fairytale wedding at St Paul's Cathedral on July 29, 1981 was a distant memory.
As part of a settlement, Charles and Diana agreed to share custody of sons, William and Harry.
Diana was reportedly awarded a lump sum of £17 million and £350,000 a year to run her private office. She was also allowed to keep her apartments at Kensington Palace.
With support for Diana at record levels, her future position may have been a worry to Charles, the next in line to the throne, which was why he was reportedly adamant that she should lose her title.
Despite her insistence, Diana was stripped of her title of Her Royal Highness, and instead became Diana, Princess of Wales.
The loss of her title meant friends or staff were no longer required to bow or curtsey in her presence, but she would now have to curtsy to her former husband, her sons and other royals.
This led to a heartbreaking conversation between Diana and a then 14-year-old Prince William that left her in tears, according to Burrell.
The young prince reportedly told his mum: "Don’t worry Mummy, I will give it back to you one day when I am King."
But almost exactly a year to the day of the divorce, August 31, 1997, Diana died in a car crash in Paris with her companion Dodi Fayed.
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