On the sad day the Queen passes away, every news organisation, magazine and paper in the world will swing into well-oiled action. The obituaries have long been written; the special editions and commemorative pull out sections designed; the TV stations already know exactly where they will each broadcast from outside Buckingham Palace.
For decades now 'Operation London Bridge,' the breathtakingly comprehensive action plan about what happens when Her Majesty dies, has been locked in and collecting dust in various drawers in London.
However despite the extensive preparation, despite the meetings and the thousands and thousands of hours spent meticulously plotting and scripting even the most minute details, there is one yawning, unknowable chasm that courtiers and HRHs cannot prepare themselves for: Will the monarchy survive once King Charles III is crowned?
Now, a new book has made a startling and portentous claim, which is that the current sovereign will go down in history as the last woman to hold that particular post. In the ominously titled, The Last Queen, esteemed journalist Clive Irving writes "Queen Elizabeth II is the longest-reigning monarch in British history and will likely be the last Queen of England."
He argues that during the Sussexes' showstopper 2018 wedding at St George's Chapel at Windsor Castle, "She must also have known that she was probably the last queen her country would ever see."
The next three heirs are all male and assuming the youngest, six-year-old Prince George, lives a hale and hearty life (those Saxe-Coburg and Gotha plus Mountbatten genes are made of stern stuff) then there will be a man on the throne for the next 80 years or so.
When the Queen passes away, a fact that is hard to square away with the relatively spritely step of the 94-year-old, there will not be another Queen regnant (a Queen who rules in her own right as opposed to the title given to the wife of the King) for the better of a century at least.
Sombre stuff indeed, right?
His case is sound and therefore all the more concerning for monarchists, palace courtiers and people who spend a considerable part of their day writing about the royal family. (Cough.)
To Irving's mind, Her Majesty has made a whopping success of her reign by becoming a regal cipher, an inherently unknowable public figure who has kept up the mystique surrounding her role by resolutely remaining "amazingly unknowable".
However to his mind, and many others, things are likely to get particularly iffy when she heads off to the big racecourse in the sky and her son becomes King Charles III, a man who to Irving has achieved the opposite of his mother: We know far too much about him.
For years on end now, we have known about everything from his enduring support for homoeopathy to his thoughts on badger culling, to the overfishing of the Patagonian toothfish, and even his occasional bouts of tampon-fancying.
While the Queen has turned dour aloofness and silence into an exquisite art form, Charles has shown no such restraint.
Irving points to the fact that the prince has notably inserted himself into several consequential architectural projects which have shaped (or would have shaped) the London skyline. (The prince, for all you modernist buffs out there, seems to fancy some sort of aesthetic return to centuries gone by.) "He is that most dangerous of meddlers who combines ignorance and opinion as a guide to his actions," Irving writes.
In 2014, "a well placed source who has known him for many years" revealed that once Charles is King, "the strategy will be to try and continue with his heartfelt interventions" in national life.
But does the UK – and the Commonwealth – really want a vocal sovereign willing to jump on his high horse whenever the mood strikes? Does this desire reflect a far more modern, engaged view of ruling or does it reek of moral superciliousness? Will this outspoken approach (which his biographer Jonathan Dimbleby calls "a quiet constitutional revolution") win over the people or simply peeve a public that probably has little interest in their King weighing in on the issues of the day?
"I think there's a really real risk that if Charles does succeed her that the monarchy will go over a cliff very fast," Irving recently told Vanity Fair. "This question of the survival of the monarchy hasn't really arisen since the time of [Edward VIII's] abdication, but it will come up as a real smack in the face.
"Charles has a serious problem … he doesn't look like an invigorating generational shift, does he?"
Assuming Charles lives as long as his mother, it will be a good two decades before his son Prince William succeeds him, so therefore the next logical question is, what shape will the monarchy be in by that point?
For one thing, will there actually be a Great Britain left for him to rule?
Over the past year, clamouring for a new Scottish independence vote has only grown with a growing chorus of Welsh voices arguing that they want out too.
Ditto, the Commonwealth. Will republican sentiment, including in Australia, finally take significant, persuasive hold under King Charles? While here we might currently view the Queen with a certain passive, apathetic affection, I'm doubtful we will be willing to proffer up the same benign acquiescence to her son as our head of state.
By the time William becomes King there may not be much left to reign. Picture: AP Photo/Chris Jackson/pool.
Sure, Charles in my book anyway, might deserve far greater public acclaim for his decades-long environmental activism (aside from his pesky penchant for private jet travel) but is that enough for us to want to keep him in the top job?
Factor in too that most likely once one of the larger Commonwealth nations such as Canada, South Africa or Australia makes the decisive move and severs ties from Old Blighty, there will be a certain contagion effect. So much for the sun never setting on the empire.
By far the biggest challenge that William will most likely inherit is having to find an answer to the question, what is the monarchy actually good for?
No really. Not to sound too much like a first-year philosophy student who has just worked out how to pronounce Descartes, but what is the point of the whole expensive, convoluted enterprise?
One hundred years ago Kings and Queens made far more constitutional sense but today they occupy some sort of strange nebulous place in modern society as sort of indentured reality stars.
They are not politicians but they play a role in public life. They are not strictly celebrities but they endure a life of unthinkable scrutiny. They are not CEOs but they preside over a multibillion-dollar brand and business. They are not entertainers but we tune in by the billions whenever one of them gets hitched and their faces move magazines off shelves like nothing else. They are not strictly philanthropists but their involvement in a cause can literally save lives.
The challenge for William is that he will have to take this mishmash of aspects of royal identity, coupled with the fact he will also be the head of a government, a religion and the armed services, and find an enduring and convincing answer as to what benefit a monarchy actually represents for Great Britain, besides shifting crate loads of Beefeater tchotkes and Buckingham Palace snow globes.
And then there's George who will ascend to the throne in about 40 or 50 years.
As recently as 2017, his uncle Prince Harry admitted that no one in the royal family actually wants to be king or queen. So, what happens if not only the public no longer buy into the notion of a hereditary monarchy but so too do the men and women given no choice about 'starring' in this never ending saga? It is not too hyperbolic to wonder for a moment, what happens if there comes a day when none of the candidates actually want to rule?
William and Kate Duke and Duchess of Cambridge are raising George and his siblings Princess Charlotte and Prince Louis as 'normally' as possible. Maybe rather than spending decades of his adult life idly waiting around for a job he never asked for, the boy might simply decide he has better things to do with his time than open parliament and oversee palace garden parties and will junk the job.
It is impossible not to feel for the Queen. Next year will mark 70 years since she came to the throne, seven decades defined by an unflagging, indomitable commitment to a gig she never wanted and to doing her duty.
To know that despite her stewardship and fealty to the Crown, the whole 1,000-year plus enterprise might yet fall apart in the not-too-distant future must be a bit heartbreaking. The fact that despite everything, despite her diligence, hard work and personal denial, it might have been for nothing reads like a Shakespearean tragedy.
You don't hear it too often these days so, long live the Queen.
There may never be another.
• Daniela Elser is a royal expert and writer with more than 15 years experience working with a number of Australasia's leading media titles.