If you ever want to see the Queen at her happiest – merrily chatting, laughing and looking as pleased as William the Conqueror when he realised they had won the Battle of Hastings and could stop for tea – then look no further than the Windsor Horse Show.
For the equine-obsessed, the show is their Mecca, a chance to ogle as much horseflesh as an excited monarch might fancy.
In normal times, it's held in Her Majesty's backyard and she attends with gusto and her signature Hermes head scarves firmly in place.
This week, the Windsor Horse Show is back on, for the first time since the pandemic, and Her Majesty had been expected to pop in on the first day, making the short drive from Windsor Castle where she now permanently lives. After all, she had a horse, First Receiver, who was competing.
According to reports, there were a bevy of royal protection officers milling about the place, the media had been penned in and an area cleared for the Queen. All that was missing was a diminutive sovereign and her charming smile …
Sadly, it was not to be.
According to the Telegraph, "at the last moment, word came from the castle that Her Majesty would not be coming after all.
"It was thought there may have been concerns over the number of photographers present, given her ongoing problems with mobility."
(There have been reports suggesting the Queen now uses a wheelchair to get around the Castle and that she does not want to be seen using said contraption by the public.)
This horsie let down is just the latest in an ever-growing list of events that the 96-year-old has pulled out of since October last year and for the first time, a new word has started circulating, a word that would essentially mean the end of her reign: regency.
Unlike abdicating, which is a wholesale quitting of the ruling gig and would immediately trigger Prince Charles' accession to the throne, a regency would mean he would rule in his mother's stead, taking over all of her official duties, while she still remained as sovereign.
A consensual regency, if you will, has never been tried before in British history.
The last time Great Britain gave a regency a whirl it was 1811 and King George III's mental decline had become such that parliament finally agreed to let his unpopular son, later George IV, take over as Prince Regent. (Popularly called "mad," or if one is to go off of the royal family's official website "deranged", some historians now argue George III might have in fact suffered from bipolar disorder.)
Unlike that situation, it is uniformly and staunchly believed the Queen's mental acuity is tip-top but this could present a perfect solution for Buckingham Palace as her continuing health woes play more and more havoc with her ability to do her day job. (One suggestion is she is experiencing heart problems along with her unspecified mobility issues.)
This week will go down in the history books as the first time that the nonagenarian had pulled out of the state opening of parliament in nearly 60 years, instead subbing in her son Prince Charles, after more than 50 years on the bench, to read her speech. (Prince William also got the nod to attend, doing his best sombre monarch-in-waiting face.)
The symbolism of the moment was lost on no one; the baton had been passed. It seems highly unlikely we will ever see the Queen slowly making her way through the House of Lords for the opening of parliament again.
This was the most glaring instance of a transition which has been quietly happening behind the scenes at the palace for years; lifelong apprentice Charles has now taken over all the most important and weighty ceremonial duties of the sovereign.
It is Charles who has attended Commonwealth Heads of Government Meetings on his mother's behalf since 2013, Charles who for the past five years has lain a wreath on her behalf at the Cenotaph on Remembrance Day, and it is Charles who now undertakes numerous investitures. (So too do Princess Anne and William.)
This week also saw the return of the Buckingham Palace Garden parties and without the news that the Queen was, you guessed it, not attending for health reasons, leaving Charles to assume hosting duties.
Charles has become King in all but name.
With the countdown to the Platinum Jubilee celebrations ticking down fast, nothing short of nuclear war will prevent this particular royal show from going on. The 5000-person jubilee pageant is ready. The corgis have been brushed. Even the self-exiled Sussexes are jetting back in for the big day.
But could the Queen be considering making the most drastic decision of her career and considering putting in place a regency after the jubilee confetti has been swept up and the crates of empties put out the back of the palace?
Her Majesty has eternally viewed abdication with the sort of disdain she would usually reserve for, I'm guessing, Peta activists, vegetarians and Prince Philip's German relatives.
But a regency? Now that's a whole other story.
"The use of the Regency Act is the first step towards abdication, which, I suspect, will happen once the jubilee is over," Clive Irving, a former Times journalist and a royal biographer told the Daily Beast this week.
That's a view supported by Duncan Larcombe, the former royal editor of the Sun.
"[The State Opening of Parliament] changed everything. The Queen really has no option if she is continually unable to perform her role as head of state … if she is now apparently incapable of doing standard, core jobs as head of state, then I think they will have to remove her, by consent of course," he also told the Beast.
Enter Robert Hardman, who penned his biography Queen of Our Times with the palace's support. As he told the Beast's Tom Sykes: "I think the issue genuinely is mobility, not something more medically troubling. But the point is that her absence at the State Opening of Parliament is not unprecedented, but the resolution to her absence — the use of the Regency Act — is."
A consensual regency would be a deft solution – think of it as a demi-abdication.
Practically, the only real outward changes would be Charles being able to order new stationery as Prince Regent and he would take over her weekly audience with Prime Minister Boris Johnson. (Now if that's not enough to put the prince off the top job …)
The Queen could still, when up to it, appear on the palace balcony or attend events like the Commonwealth Day Service at Westminster Abbey.
Most importantly, it would give the poor woman a break. (In pretty much any other circumstance, a 96-year-old still being expected to turn up for work every day would see Social Services involved, quick sticks.) She could devote more time to her passions, like the gee-gees, and spend more time with her beloved great-grandchildren.
Moreover it would be a dignified final chapter to a historic reign, rather than this sad shrinking version of a Queen and a historic reign we are currently witnessing.
For now, it's time to get started on your coronation chicken sandwiches and to order bottles of Pimms as enthusiastically as Princess Margaret sprinting towards the drinks trolley. But a month from now? The royal landscape could look very different.
• 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.