Queen Camilla dazzled royal fans on Tuesday evening when she arrived at Windsor Castle wearing the unexpected Greville Emerald Kokoshnik tiara - famously worn by Princess Eugenie at her 2018 wedding.
This sparkler is one of the most popular British royal tiaras of all time due to its stunning beauty.
Boucheron, a French luxury jewellery house, designed the tiara in 1919 for Dame Margaret Greville, hence its name.
Dame Margaret subsequently gifted the fascinating piece of jewellery to the Queen Mother in 1942, which explains how it found its way into the hands of the Royal Family.
The tiara was photographed on Dame Margaret a few times, but was not properly seen again until 2018, when Princess Eugenie walked down the aisle at Windsor Castle to marry Jack Brooksbank.
The diamond and emerald tiara features a large cabochon emerald as its main jewel.
Its design was inspired by the kokoshniks that were popularised by the Romanovs.
The Queen Mother kept the sparkler in her possession until she died in 2002.
Queen Camilla reminds fans of Princess Eugenie's royal wedding with 'unexpected' choice
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Queen Elizabeth II subsequently inherited the piece of jewellery, and later loaned it to Princess Eugenie for her nuptials.
As it was on loan to Eugenie, the 35-year-old does not officially own the sparkler.
This would also explain why Queen Camilla was able to choose the tiara from the Royal Vault to wear on Tuesday evening.
Her Majesty paired the Greville Emerald Kokoshnik piece with a cream embroidered dress by Fiona Clare, one of her favourite designers.
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Queen Camilla paired her tiara with a Fiona Clare dress
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Camilla additionally wore a diamond serpent necklace and diamond earrings.
Royal fans were ecstatic at the sight of Eugenie's wedding day tiara making a reappearance on the Queen's head.
One wrote on X: "This tiara is one of the most beautiful in the collection. I’m glad Camilla is dusting off the jewellery."
Another commented: "Oh my heavens, doesn't Her Majesty look wonderful! I LOVE seeing a different tiara on her and that one looks really terrific on her!"
Jack Brooksbank and Princess Eugenie on their wedding day in 2018
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Similarly, someone said: "Woah!! Wasn’t expecting this but I LOVE IT!!
"Queen Camilla is wearing the Grenville Emerald Kokoshnik Tiara tonight at the Diplomatic reception!!
"Fingers crossed for more tiara outings in the future for this one!"
Finally, a royal fan posted: "GOOD. That tiara is too damn beautiful to not be seen again!"