When Prince William and Prince Harry were young, not-so-carefree and spent every spare evening dutifully plumbing the depths of the drinks menus at Boujis and Mahiki, Mayfair's go-to watering holes for the titled and the entitled, the boys had a trick they used to deploy.
They would purposefully plant fake stories among their friends to see if anyone was leaking to the tabloids.
Trying to maintain their privacy was a mainstay of their lives, something that the royals' chums, girlfriends and staffers would have been intimately aware of.
And this is the bit where we get to the slightly twisted irony. This week various groups who once made up Harry's inner circle are reportedly considering committing what used to be the ultimate sin in the eyes of any self-respecting HRH and speaking out about him.
Both William and Harry enjoyed decades-long friendships with boys they have known since they were sent to Ludgrove prep school at age 8.
Not a single one has ever sold Harry out and dished on the princes' lives, no matter the very large, oleaginous cheques the tabloid press would have, I'm assuming, waved enticingly in their direction (stately homes aren't cheap to heat, you know).
All that could be about to change, with Harry's mates allegedly threatening to mutiny and dish the dirt if the royal should reveal too much about their younger days in his forthcoming, as yet untitled memoir.
"There is a fear that he's going to reveal details of his hedonistic youth which some worry will play havoc with their careers and personal lives," a friend has told the Daily Mail.
"Harry's mates have remained loyal to him … so far," another warned.
"If Harry slams any of his old school and military buddies in his new book they have pledged to break ranks to tell their story," a source told the Mail.
The possible dirt they might have on the now-Duke of Sussex and green juice-swilling father-of-two boggles the mind.
However, Harry could have bigger problems than a clutch of pasty men who can trace their forebears back to the Norman invasion suddenly indulging in a spot of public truth-telling.
The last serious relationship Harry had before meeting then-Suits star Meghan Markle (and now wife, the Duchess of Sussex) was with Cressida Bonas. The couple dated from 2012 to 2014 before she reportedly ended their romance after becoming "spooked" by watching the scrutiny and pressure on Kate, the Duchess of Cambridge.
In the years since then, Cressida has become a successful actor in the London theatre world and has done numerous interviews, all very politely skirting over even mentioning her royal ex.
Again, could that be about to change?
The Daily Mail's society columnist Richard Eden has reported that, according to a friend of the aristocratic thespian, Cressida was left "shocked" by the news that Harry is penning a memoir; however, "perhaps she'll be tempted to write about it now. She could give a different perspective on the relationship."
While the chances of this coming to pass are slim given Cressida has been nothing but impressively discrete about her Harry romance, the very fact that this question is even being publicly pondered for the first time is noteworthy.
Just in case the possibility of his former friends becoming loose-lipped isn't enough of a worry, Harry's tell-all could also potentially see royal aides given the green light to hit back and to publicly talk about experiences working with Harry and Meghan, according to the Daily Mail.
The Sun's former executive editor Dan Wootton, who broke the news that the Sussexes intended to quit full-time working royal life last year, has reported that "furious former staff members" of the couple "are hoping the Duke's tell-all autobiography will finally allow them to speak out against the royal couple without the fear of repercussions".
"Harry and Meghan's former staff members are convinced that this book is being written to settle scores and will likely include a lot of detail about their time within the royal family," a royal insider told Wootton.
"Conversations have already started about what steps they might be able to take to protect their own reputation and that of the monarchy post-publication."
While palace staffers and courtiers are all covered by hefty confidentiality agreements, the insider said, "there may be a provision given to staff members to respond to any claims that they consider to be inaccurate".
"Maybe a blind eye could be turned if staff members used friends or family members to correct the record on their behalf. These are the sorts of conversations going on at the moment," they said.
All of this is before, of course, the royal family themselves have marshalled their resources and taken some sort of steps to counter whatever new and damaging revelations Harry might trawl out. (No one gets $27 million for writing long, detailed chapters about how scrummy Balmoral is or for revealing that Princess Anne is a whiz at charades after her third sherry.)
So, where does that leave things?
While Harry might have nabbed a reported $27 million advance for his autobiography, it's looking increasingly like he has also opened a can of worms. (His publisher Random House has said that "proceeds" from the title will go to charity; the New York Post's Page Six column has reported it is unclear whether that will include the advance.)
Thus far there have only been two key parties in the ongoing Megxit soap opera, one in Montecito, the other in London. If Harry does decide to write about his former wild ways with the lads or his relationship with Cressida or details that implicate particular palace staffers, it could open the floodgates to a whole gaggle of new players in this mucky PR fray.
B.S.E – Before the Sussex Era – breaking the unspoken vow of silence all royal confidants are expected to faithfully adhere to would have only resulted in immediate banishment from the inner circle.
Take the tragic case of Marion "Crawfie" Crawford, the Queen's adored childhood nanny (she was such a beloved maternal fixture in Her Majesty's life, Crawfie was only given permission to retire from royal service just before the royal herself wed at the age of 21).
What Crawfie is best known for is the fact that in 1950 she wrote a book about her famous charges called The Little Princesses.
Though there is some debate about what role the Queen Mother might have played in the book's genesis, Crawfie, for her effrontery in pulling back the curtain on the Windsors, was swiftly and immediately excommunicated from royal life and not a single member of the family ever spoke to her again. She was utterly devastated.
Spilling the royal beans used to be the ultimate transgression, but now that we are firmly wedged in the Sussex Era, when precedent has long since gone out the window, we are facing the possibility of a damaging tit-for-tat mudslinging.
The truth is supposed to set you free. If there is one thing we've learned this year, that doesn't appear to hold true if you happen to be an HRH.
• Daniela Elser is a royal expert and a writer with more than 15 years' experience working with a number of Australia's leading media titles.