There are 36 tiaras in the royal collection. Of the glittering toppers stashed away somewhere in Buckingham Palace, several are particularly famous.
There's the Queen Mary Fringe Tiara worn by the Queen on her wedding day and more recently by her granddaughter Beatrice for her backyard "I do's". There's the truly enormous Greville Tiara which – get this – was given to the Queen Mother by one of her mates.
And then there's the Cambridge Lover's Knot tiara, a splendid confection of diamonds and pearls that date back to 1913 and which for 15 years was regularly worn by Diana, Princess of Wales.
However, tiaras aren't just lovely and useless totems of wealth and privilege – they have caused quite the ruckus in the House of Windsor of late.
Rewind to 2018, when veteran royal reporter Robert Jobson first alleged that Meghan Markle, in the lead up to her wedding, had gone into a strop after her request to wear the Greville Emerald Kokoshnik Tiara on her big day was turned down by the Queen.
An enraged Prince Harry then allegedly uttered the immortal line, "What Meghan wants, Meghan gets."
This particular story was soon embellished; the reason for the tiara turn down was because another royal bride, Princess Eugenie, had already bagsied it. Another version of this particular tale alleged that the piece's questionable Russian provenance meant it was not a suitable candidate.
(Makes you wonder: What other priceless, potentially dubiously acquired treasures does Her Majesty have stashed away in the bowels of the palace?)
Now, we have been offered yet another take on this monarchical meltdown. The Daily Mail has reported that things started to heat up when Meghan flew her hairdresser to London for a pre-wedding trial run and she called the Queen's longtime dresser Angela Kelly to get access to the tiara.
Kelly, who was not at Buckingham Palace but Windsor Castle, turned down the request.
"Angela essentially said, 'I'm very sorry, that's not how it works.' There's protocol in place over these jewels. They're kept under very tight lock and key. You can't turn up and demand to have the tiara just because your hairdresser happens to be in town," a source told the Daily Mail.
"Harry was very quick to let everybody know of his anger and frustration," another royal source told the Mail, prompting the Queen to reportedly "scold" her grandson for the way he had spoken to Kelly.
Now, we could chalk this up to another unflattering episode in the Sussex melodrama if it wasn't for an allegedly malicious coda to all of this.
According to the Sun's Dan Wootton, after this tiara imbroglio, "William and … Kelly, were united in their decision not to loan Meghan items from the Royal Collection, which included tiaras worn by Diana".
(Here's a quick Tiara 101 rundown. They can only be worn by married royal women, hence why the first occasion that Kate got to wear one, namely the comparatively modest Cartier Halo Tiara, was for her big day.
They can also only be worn for weddings or white tie occasions, thus being a Duchess doesn't mean you can simply grab one whenever you fancy to add a bit of sparkle to your look. Lastly, with a few key exceptions, the most famous tiaras, necklaces, bracelets, brooches and earrings worn by Windsor women are not owned by them personally but belong to the Royal Collection. The Queen sometimes offers pieces from the collection on a long term loan basis to royal women.)
The question of whether Meghan would have been allowed to borrow jewels from the Royal Collection is a moot point because during her 20-month stint there was no appropriate occasion.
Prior to the Sussexes sullenly and impetuously announcing they were done with royal working life in January, there was only one white tie affair – the June state dinner for Donald Trump. Meghan was on maternity leave at the time and given the President's horrifying p*ssy-grabbing braggadaccio, I doubt she was in a rush to gown-up to celebrate.
However, that's not the point, rather this is about the glaring double standard at play.
The alleged decision to bar the Duchess from wearing pieces from the collection has the bitchy air of a monarchical Mean Girls clique.
If, and it's a big if, William and Kelly did band together to prevent Meghan from having access to the Royal Collection, it not only makes them look petty and vindictive but deeply hypocritical.
Again, if we take the Daily Mail story at face value, yes, Meghan was seemingly showing a wilful disregard for the way things get done in the royal family. (In short: You need an appointment to do anything.)
But of all the qualities that define royal life, a nearly religious fealty to protocol stands out. Assiduously adhering to rules is the Windsor way thus for William and Angela to capriciously (allegedly) change the guidelines out of animosity towards one person totally undermines their moral authority here.
Whether some members of the royal family or the palace machine liked it or not, after her wedding Meghan was a Duchess, married to the sixth-in-line to the throne and an HRH. Her rightful claim to be able to, when appropriate, borrow pieces from the collection should have been a given.
Kate, after all, gets to borrow pieces and perhaps none more high profile than the Cambridge Lover's Knot Tiara when, after nearly two decades locked away, she wore it in 2015. (Since then she has worn it on at least five occasions.)
Kate and the tiara's most recent outing came just before Christmas when she attended the annual diplomatic reception at Buckingham Palace, pairing the whopper with a black velvet dress.
How must Meghan have felt seeing those shots of Kate wearing such a historic and symbolism-laden tiara?
Here was her sister-in-law, regularly held up by the press as the very essence of duchess perfection, wearing an important piece lent to her by the Queen. Here was Kate with a glittering, prized token of regal approval that Meghan – had she wanted or had the opportunity to ask to wear something similar – may well have been denied?
Did Meghan, looking at the Cambridge Lover's Knot Tiara, see a priceless symbol of her ostracism from the Windsors?
Perhaps the takeaway here is, if you want the perks of royalty you have to play by the rules at all times; renegades don't get access to Royal Collection.
Meghan only wore a tiara once. Now that she and Harry have quit official royal working life, there is little chance she will ever be given the opportunity to rummage around the Queen's tiara cupboard.
Still, I wonder if she would actually want to wear one. As she and Harry gear up to launch their new charity Archewell next year, I think she might be more interested in donning a halo instead.