Princess Diana once confronted Camilla over her affair with Prince Charles in one of her "bravest moments" on a night where "all hell broke loose".
The People's Princess clashed with her love rival, known at the time as Camilla Parker-Bowles, at a birthday bash for Camilla's sister Annabel Elliot in 1989.
After the face-to-face clash at the "ghastly" event, Prince Charles ran off like a "headless chicken", Diana once said.
In a conversation recorded at Kensington Palace in 1991, Diana said the run-in was "one of the bravest moments" of her 15-year marriage to Charles.
After their split, the late Princess famously called Camilla the "third person" in her marriage.
Diana's face-off with Camilla came three years before the couple split in 1992, and seven years before their official divorce in 1996.
“I walk into the house and stick my hand out to Camilla for the first time, and think ‘phew got over that,’” Diana said.
The Princess, who was 20 when she married a 32-year-old Charles, had earlier that day decided she would attend the “ghastly” event despite nobody expecting her to turn up.
“He [Charles] needled me the whole way down to Ham Common, trying to bait me,” Diana said.
“‘Why are you coming tonight?’ Needle, needle, needle the whole way down. I didn’t bite, but I was very, very on edge.”
Diana had also told herself she would not greet Camilla with a usual kiss hello, but instead a more formal handshake.
“This was my big step,” she added.
Meanwhile once inside the party, Diana suddenly noticed there was no sign of Camilla or Charles.
She said the realisation ‘disturbed her’ and she then went searching for the pair in another part of the house.
“I know what I’m going to confront myself with,” she admitted. “They tried to stop me from going downstairs. ‘Diana, don’t go down there.”
But Diana replied: ‘I’m just going to find my husband.’
She said she found a “happy little threesome going on” with Charles, Camilla and another man chatting away.
“I thought, all right, this is your moment, so I went and sat down and joined in the conversation as though we were all best friends,” Diana continued.
“And I said, ‘Camilla, I’d love to have a word with you, if possible.’ And she got really uncomfortable, put her head down and she said, ‘Oh yes, all right.’
“And I said to the two men, ‘Ok, boys I’m just going to have a quick word with Camilla, and I’ll be up in a minute’.
“They shot upstairs like chickens with no heads and I could feel, upstairs, all hell breaking loose. ‘What is she going to do?’
“So I said, ‘Camilla, would you like to sit down?’ So we sat down and I was terrified of her. And I said, ‘Camilla, I would just like you to know that I know exactly what’s going on’.
“She said ‘I don’t know what you’re talking about.’
“I said ‘I know what’s going on between you and Charles, and I just want you to know that.’
“And she said to me, very interestingly, she said to me, ‘You’ve got everything you’ve ever wanted. You’ve got all the men in the world falling in love with you, you’ve got two beautiful children, what more do you want?’
‘I want my husband,’ Diana said she replied.
She added to Camilla: “Don’t treat me like an idiot.”
On the car journey home, Diana said Charles was over her “like a bad rash.”
“I cried like I have never cried before,” she said, adding it was seven years of pent-up anger coming up.
However, the next morning she felt a tremendous shift.
“I’d done something, said what I felt,” she added.
She said she told Charles there were ‘no secrets’ and he could ask Camilla exactly what their conversation had been.
Diana and Charles’ relationship eventually announced their separation in 1992.
Their divorce was confirmed in 1996 and Diana died in a car crash in Paris in 1997.
Charles, now 71, went on to marry Camilla, now 72, in 2005.
In a message to the nation yesterday, the Queen wrote about her wish for Camilla to take on an "extraordinary" title once Charles takes the throne.
In a statement, she said: “When, in the fullness of time, my son Charles becomes King, I know you will give him and his wife Camilla the same support that you have given me.
“And it is my sincere wish that, when that time comes, Camilla will be known as Queen Consort as she continues her own loyal service.”
Speaking of the Queen's announcement yesterday, BBC Royal Correspondent said: “This is the most extraordinary message.”
“For Camilla, the journey from being the third person in a marriage to queen-in-waiting, is complete.”
The Queen and Camilla did not see eye to eye for a very long time, mainly due to her relationship with Charles.
But the "extraordinary" move to dub her Queen Consort shows the contempt has "evaporated completely", according to the Queen's former press secretary, Dickie Arbiter.
He added: “The Duchess has shown that she is a great support to Charles, the Queen and the institution.”
Royal author Dr Andrew Lownie said: “Camilla has earned her spurs. The Queen, who wouldn’t have Camilla in the room at one point, has become very fond of her.
“I think there’s a real sense of the passing on of the crown.”
The Queen’s heartfelt announcement ran to 385 words. Of February 6, 1952, she wrote: “It is a day that, even after 70 years, I still remember as much for the death of my father, King George VI, as for the start of my reign.”
She spoke of a “sense of hope and optimism” in her Platinum Jubilee year and thanked “people of all nationalities, faiths and ages” for the goodwill and support they had expressed.
The Queen wrote fondly of her late husband, adding: “I was blessed that in Prince Philip I had a partner willing to carry out the role of consort and unselfishly make the sacrifices that go with it... a role I saw my own mother perform during my father’s reign.”
The Queen, signing off as “Your Servant”, added: “I look forward to continuing to serve with all my heart.”
It was her reference to Camilla that grabbed the world’s attention last night. The issue of her title had been a delicate issue for two decades.
