Princess Alexandra married Bertie, the Prince of Wales, and the couple later became Queen Alexandra and King Edward VII.
This is how the brooch eventually found its way into Diana’s jewellery collection.
Although Diana and Camilla wore the brooch in different ways, it is no surprise that some royal fans and experts have suggested the situation is rather strange.
Charlotte White, Head of Design at Europe’s largest online diamond jeweller, 77 Diamonds, said: “The notion of Camilla wearing a sparkling emerald and diamond brooch that once rested gracefully as a pendant on Diana’s skin and close to her heart, does feel somewhat jarring when you think that many years ago Camilla was Diana’s husband’s lover.”