Grabbing this rare opportunity to post from my favourite royal jewels category called "If you've got 'em flaunt 'em".

Queen Alexandra, at possibly the last State Opening of Parliament for Edward VII's reign (Feb 1910), wore Cullinans I and II as a brooch. I believe Cullinan VI, which he bought for her, is above and suspended from her collier résille.



But Queen Mary was able to outdo that when her turn came.
Four months later in June 1910 she was presented with the rest of the Cullinans.
At a later State Opening of Parliament Queen Mary wore two Cullinan brooches.

Cullinans I and II form the lower brooch and III and IV appear suspended from the bottom diamond rivière. She is wearing another on the band of her circlet. I and II could be removed from the sceptre and Imperial State Crown on request.



Here is a link to the story of how the second group of Cullinans were set by Collingwood for the Government of South Africa to present to Queen Mary, as brooches and a ring.
https://royaljewelslists.boardhost.com/viewtopic.php?id=421