For the upcoming south korean state visit to london i guess what Camilla, and possibly also Catherine will wear depends on if they recive an order from the president.
During the south korean state visit to Sweden 4 years ago, both Queen Silvia and Crown Princess Victoria recived the Order of Diplomatic Service Merit.
If Queen Camilla and The Princess of Wales will recive that too, they will be wearing a pink sash.
If so i can see Queen Camilla wearing the Belgian/George VI Sapphire Parure… Or perhaps debut the Dubai Looped Sapphires…
I would love to see Queen Mary’s/Princess Margaret’s Sapphire bandeau re-appear on Catherine… If it doesn’t, i would love to see her wear her coronation dress with the Lotus Tiara, The Greville Sapphire Fringe Earrings, King George VI Festoon Necklace, and Empress Marie Feodorovna’s Sapphire and Pearl Brooch.
For the others i guess -
The Duchess of Edinburgh : Wedding Tiara and diamonds from Queen Elizabeth.
The Princess Royal : Diamond Festoon Parure.
The Duchess of Gloucester: Gloucester Honeysuckle Tiara with emeralds or pink topazes to the State Banquet / Teck Turquoise Parure to the Guildhall Banquet
Princess Michael of Kent (if she attends) : Kent Festoon Tiara.
Princess Alexandra seems to have retired now. And with her mobility issues we saw at the coronation, i don’t think she will attend any more banquets
But i will be more than happy if i’m proven wrong !