I agree with PaulP. The items which are said to be "heirlooms of the crown" are private property. The difference between them and say Her Majesty's engagement ring as an example is that the "heirlooms of the crown" are held in trust for the use of queens. That means that a Queen who has the right to use the jewels cannot leave them to her favourite person, charity etc.


None of us has ever been privy to the precise conditions under which heirlooms of the crown can be used, but the fact that George VI gave QEII the Crown pearls as a wedding gift while she was still a Princess suggests that the reigning monarch has some discretion over who can wear or use the jewels.

Heirlooms of the crown are in a totally different category from the Crown Jewels/Regalia.