The Duke and Duchess of Sussex "stepped back" from the Royal Family in 2020, relocating to California to live in an £11million Montecito mansion.
But before the couple were officially an item, Meghan was asked to appear on the cover of Vanity Fair's September 2017 issue.
The magazine ran with the headline 'Wild About Harry' on its front page – choosing to focus on the former Suits star's relationship with the prince, rather than her charity work.
When pre-publication copies were sent to the Palace, Meghan is said to have reacted "hysterically" as she "furiously" phoned her PR firm.
Meghan Markle and Prince Harry
PIROSCHKA VAN DE WOUW
Meghan Markle
DYLAN MARTINEZ
Tom Bower – journalist and author of 'Revenge: Meghan, Harry and the war between the Windsors' – says the Duchess' unexpected openness about Princess Diana's youngest son took royal aides by surprise.
He writes: "Like a thunderclap, the interview triggered sensational reactions: Meghan had used her relationship with Harry to promote herself.
"The Hollywoodisation of the Royal Family had sealed Meghan's fate as Harry's fiancée."
In the 2017 culture magazine, Meghan said: "I'm sure there will be a time when we will have to come forward and present ourselves and have stories to tell, but I hope what people will understand is that this is our time.
"This is for us. It's part of what makes it so special, that it's just ours. But we're happy.
"Personally, I love a great love story."
Mr Bower, whose book is being serialised by The Times, reports that Meghan was furious when Vanity Fair chose to lead their feature on these quotes, arguing that the piece should have been focused on her philanthropy.
But the author says this was due to the fact that researchers were unable to substantiate two key stories she had told them about her activism.
The interview was organised by Keleigh Thomas Morgan, a partner at Meghan's PR firm Sunshine Sachs.
It was conducted by Sam Kashner – a contributing editor at Vanity Fair, who admitted before the interview that he had no idea who Meghan was.
Mr Bower claims the journalist was under strict orders from Harry to steer clear of sensitive subjects such as race, Donald Trump and the couple's romance.
When the magazine chose to feature Meghan's comments on Harry so prominently, Mr Bower writes that Mr Kashner later recalled: "She complained because she wasn't presented in the way she wanted.
"She demanded the media do what she expected. I felt manipulated."