Somehow they look much smaller on the DoCam though. My time here has taught me never to put things pass the BRF in that they could well be a tiara related to the set but it's just the at times jewel shy Queen has not dawned it to our knowledge.
I recall it was said the Queen had removed I think 3/4 stones from the necklace and possibly a ring and had them worked into a new bracelet. So the question is are they loose stones from the set and was their an original bracelet given along with the set meaning that if HM created another bracelet from the too long necklace and a ring then one can deduce their is still the original bracelet about.
But given that HM has reportedly 2 sapphire tiaras of her own and possibly another and it is unclear whether or not her mom the late QEQM had any from the Greville bequest I'm unsure they may want to have another sapphire tiara in the collection.
What would be nice is to have an outing of the pearl and sapphire/ diamond necklace which basically formed the memory of the late Diana PoW along with a magnificent tiara to go with it unless it would be felt that a tiara would have to really stand out to blend in with such and overpowering statement peice.
A good match for tiara for either that famed sapphire necklace or the Dubai set would be the Grand sapphire tiara in the Wruttingburg, 'hope I spealt their sir name correctly; from the family collection, the stones are huge and beautiful and would match up well with the stones of the two sets I just mentioned.
It is possible that William could do some gift of an outstanding Headpiece for his dutiful wife of sapphires as he basically gived her his late mom's sapphire engagement ring.
But to me the PoW is more into history, jewels and grandure than his sons and may well be the one to really bring out or create statement pieces going forward.