The diamond Kokoshnik tiara, which was created in 1888, actually pulls double duty—though Camilla wore it on her head, she could have worn it as a necklace, as the Garrad Royal Ledger states.

We tried on a £295,000 diamond and pearl necklace and a £100,000 diamond tiara. We visited London jeweller Bentley & Skinner, which specialises in buying and selling rare antique jewellery.

February’s birthstone, the amethyst, is found across royal jewellery collections. However, it is the Swedish royal family ...