I found this great site with tones of information 'The Royal Magazine' and became glued to same as I'm off work for the bank holidays. In this link one will see that many fine and beautiful jewels left the British Royal family when members married out into other noble or royal families.

https://royal-magazin.de/german/hessen/hesse-sapphires-diamond-alice-halsband-schmuck-royal-jewels.htm

Also an interesting tiara below.

https://royal-magazin.de/german/hessen/hessen-margaret-topas-tiara-koch-geddes.htm

Regards,

Dave.