The story of how the biggest royal expose in history came to be began in a transport cafe outside of London over bacon and eggs in 1991.
According to Diana's biographer Tina Brown, it was there that a young journalist named Andrew Morton and one of the Princess' longtime friends, Dr James Colthurst, first met. Over the next 10 months, Colthurst would act as a go-between, ferrying interviews Diana recorded on cassettes to Morton as he worked on a book about her.
Diana knew the book's publication and its revelations about her eating disorder, suicide attempts and details about Charles' infidelity would be incendiary. However, by all accounts, she made the decision to participate because she felt that going public once and for all was the final, desperate move she could make.
After a decade trapped in a farce of a marriage to a man whose love lay elsewhere and after years chafing against the starched rigidity of a, in her opinion, deeply uncaring family, dramatically revealing her full hand was the last, most audacious play she had. As Brown writes: "Diana's friends … believed that she faced a choice – explode or implode."
When the book was first excerpted in 1992 in the Sunday Times it sent shockwaves through the royal family, Britain, and the world, leaving the public transfixed by the tell-all which ripped away the discrete curtain that had protected Windsor life. Gone was discretion and the veneer of royal amiability, and here was a decade's worth of fury and searing hurt which immediately dealt the monarchy's image a severe blow.
While Morton's book firmly put public favour on Diana's side, forever affixing the victim's mantle to her shoulders, it infuriated the royal family and ultimately doomed her relationship with them.
This particular history lesson is worth keeping in mind given the news that a new biography of Harry and Meghan, the Duke and Duchess of Sussex, will soon hit the shelves. On August 11, Finding Freedom: Harry and Meghan and the making of a Modern Royal Family, will be released.
New details about the book, written by Omid Scobie and Carolyn Durand, two royal reporters known to be sympathetic to the couple, emerged over the weekend when it was listed for pre-order online (based on pre-orders it's already a bestseller on Amazon).
According to the book's description, the hotly anticipated title will go: "beyond the headlines to reveal unknown details of Harry and Meghan's life together, dispelling the many rumours and misconceptions that plague the couple."
While the Daily Mail reported last week that Harry and Meghan themselves had been interviewed for the book, the newly unveiled details instead promise that the authors had "unique access and written with the participation of those closest to the couple".
What that realistically translates to remains to be seen but this book has the potentially to be as equally explosive – and potentially damaging – as Diana's book.
While we don't know quite what level of co-operation there was between the couple, their inner circle and the authors, this biography could also potentially open Harry and Meghan up to accusations of hypocrisy.
Let's start with the tome's title because, just what exactly are the Sussexes "Finding Freedom" from? The royal family might be a stiff lot who eschew hugging and enjoy slaughtering small birds for sport but they are generally seen as a benign, if dull, bunch.
Likewise, royal life might be a combination of the tedious (Buckingham Palace garden parties which require hours of making tortuous pleasantries) and the stultifying (hours spent stomping across vast Scottish moors in the rain in summers) but it is hardly as if they were trapped behind enemy lines or suffering behind bars.
If The Firm is so abhorrent, why are they still resolutely using their titles, including liberally sprinkling them through official communiques? If the monarchy was something that they needed to escape, why still keep a property on the Queen's Windsor estate and accept money from Prince Charles?
Also, if per the authors, the couple are "determined to create a new path away from the spotlight" why have they moved to the paparazzi capital of the world?
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Various members of the royal family have co-operated with friendly journalists and writers over the years – including Prince Charles and Prince Philip – but these efforts were essentially blatant PR gambits to cast the particular HRH in a flattering, rosy light.
Here, the choice of title seems to suggest that this work might go beyond simply extolling the wonders of Harry and Meghan and could potentially take aim at the monarchy as well.
If Finding Freedom does offer up an inflammatory view of the royal family, emphasis on if, and it is apparent that the renegade couple have in any way collaborated with the authors, then this would be straying into particularly dangerous territory. This sort of move could seriously damage, perhaps fatally, the already delicate relationship between the Sussexes and the Windsors.
If this is the case, it would seem likely that they (like Diana and Fergie before them) would find themselves pushed to the periphery of royal life and would be the death knell for any future reunion with the Queen and Co.
And that is leaving aside the fact it would be deeply hurtful, especially for the Queen and Prince Charles as both Harry's grandmother and father and given they have both worked tirelessly for decade upon grinding, dull decade in service to the monarchy.
No matter what salacious details or not are offered up in this biography, news of its imminent arrival will surely be about as welcome behind Palace gates as a troop of PETA's most ardent supporters at a Sandringham shoot.
The book's publication will most likely set off a global media storm, even if that just means having to contend with a grab bag of already-run rumours being rehashed in thousands of news reports.
Given the royal family is currently enjoying a particular purple patch in terms of public support thanks to their chipper efforts during the coronavirus crisis, this sort of messy personal media squall is exactly what they would be desperate to avoid.
While the couple has yet to confirm or deny their involvement in Finding Freedom, or to comment on it at all, August 11 looks likely to be a particularly nerve-racking day on both sides of the Atlantic. The stakes have never been higher.
• Daniela Elser is a royal expert and writer with 15 years experience working with a number of Australia's leading media titles. This article was first published on news.com.au.