9. The Tiara of Greville
on the Duchess of Cornwall, Camilla
Been in possession since 1942
Value Estimate: Not Known
The history of how the royal family acquired this tiara is fascinating: after her death, Lady Greville, a longtime friend of the royal family, left the queen her whole collection of jewels. She publicly revealed that the family-brewing business is how she got rich.

The Greville Tiara Camilla, Cornwall’s Duchess ©2012 by Chris Jackson via Getty Images
Among them was the stunning Greville Tiara. The Queen Mother and, more recently, Camilla, Duchess of Cornwall, both regularly wore the tiara. Diamonds are used to accentuate the design, which was designed by Boucheron in 1919 and features a distinctive honeycomb pattern.
