There isn’t any ‘protocol’ per se.
There is a lot of confusion regarding the jewellry.
The Crown Jewels are kept in the Tower of London.
They are only worn on state occasions.
They belong to ‘the state -aka the people’.
They include Cullinan l & ll.
They cannot under any circumstances leave the United Kingdom.
During the war they were removed from the tower, well wrapped up, put in waterproof tins and buried under the dungeons at Windsor Castle.
Then we have the jewels that we see the Queen and Members of the royal family wear.
This is privately owned by the king, up to him what he does with it, who wears it etc. If he wanted to sell the lot he could.
Theres is no trust, no protocol, simply tradition.
For example, the Oriental circlet had only been worn by Queens. QV, Queen Alexandra. Queen Mary, Queen Elizabeth and Queen Elizabeth ll.
Then all of a sudden there it was onthe head of the Princess of Wales.
This is because there is no ‘protocol’. Whoever owns them decides who can wear what.
Catherine will likely never ‘own’ her own tiara. She wears/has worn the Cartier scroll tiara (on her wedding day), the Lotus Tiara, the Cambridge lovers knot tiara, and since the death of QEII she has worn the Strathmore Rose and the Oriental circlet.
Princess Anne, Sophie Edinburgh, Duchess of Gloucester , Duke of Kent all hve their own tiaras. There is a likelihood though that some of Anne’s tiaras are long term loan and would on the occasion of her death return to the Royal vault. I suspect this is the case with the Greek Meander Tiara. It was a piece that belonged to Prince Philip’s mother. When Anne dies l suspect Peter and Zara will have to hve an auction of ‘stuffs to pay the IHT. Gatcombe is a working farm-but who knows what the IHT will be on working farms? It may pass IHT free.
But I doubt Anne has enough liquid funds in her estate to pay the IHT on the estate as the jewellry alone will be worth millions purely because of its royal provenance.
I don’t think the RF will want to see pieces which have historical/sentimental value going to auction. So I believe the Greek tiara will meander its way back to the jewel room at BP. When Margaret’s children picked out what would be sold to cover her death duties they sold the Poltimore. I don’t blame them - they might never wear it, insurance would cost a fortune . But the other tiaras Margaret wore -the lotus, the Persian turquoise, the Cartier scroll and the Teck circlet tiara - they were not sold. So they went back to the vault and we know this as two of them hve been worn by Catherine.
Yes, there are lots of tiaras which don’t get worn.
Ten years ago we had never seen the Greville Emerald Tiara (The one Eugenie wore) and hadn’t seen the one Meghan wore for over 80 years. Ditto the Strathmore rose.
I’ll do a post soon of the tiaras in the ownership of the king.