It was a glittering occasion as King Charles III , Queen Camilla and Prince William welcomed senior diplomats to Windsor Castle for the annual Diplomatic Corps reception on Tuesday night.

The Queen looked resplendent in a Fiona Clare couture creation, which she paired with the Greville Emerald Kokoshnik Tiara, once owned by Queen Elizabeth II and now better known as Princess Eugenie 's wedding tiara. The Queen finished her look with a pair of sparkling diamond earrings and her favourite serpent necklace – a trio of diamond accessories that lit up the state room.

Yet there was another eye-catching detail on Her Majesty's dress: The Royal Family Order of King Charles. But what is this subtle ornament with such an esteemed history?

The bestowal of a Family Order, a portrait of

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