The mystery of Queen Camilla's state banquet necklace

A mystery was afoot at the state banquet on Tuesday evening. King Charles, Queen Camilla, Prince William and the Princess of Wales rolled out the royal red carpet for the Sultan of Oman at Windsor Castle, joining Princess Anne and the Duke and Duchess of Gloucester for an evening of pomp and circumstance, adorned with gowns, tiaras, and a whole host of heirloom jewels.

But there was one piece that truly stood out among the crowd – for its glided glamour, yes – but also for the way it had royal watchers scratching their heads long after the candles had been snuffed out in the Windsor Castle dining room. What necklace was Queen Camilla wearing?

The Queen certainly put on a regal display at the banquet, donning the Girls of Great Britain and Ireland tiara – the most famous diadem worn by Queen Elizabeth II, who chose it for more royal engagements than any other and even chose it for the portrait used on British currency throughout her 70-year reign. Her Majesty paired the piece with a royal blue gown and the Kent Amethyst earrings, some of the oldest pieces in the entire royal vaults, which date back to Princess Victoria, Duchess of Kent, Queen Victoria’s mother.

But what necklace was Her Majesty wearing? Seemingly crafted from amethysts and diamonds, the glorious collection of jewels is of an entirely unknown provenance. Some royal watchers wondered whether the piece might have been a gift from the Sultan of Oman, though the presents exchanged between heads of state on such visits tend to be significant more for their cultural significance than monetary value.

One’s thing for certain: the royal women have been into amethysts of late. The Princess of Wales donned a rarely seen sautoir adorned with a heart-shaped stone, suspended on three rows of pearls, interspersed with oval amethysts with a diamond surround – it has been in the royal vaults for generations, but has very rarely graced the public eye.

Originally, the show-stopping jewels were owned by Queen Alexandra, the wife of King Edward VII and the mother of George V. In 1923, it was presented to Lady Elizabeth Bowes-Lyon (the future Queen Elizabeth, Queen Mother) on her wedding to the Duke of York (later King George VI). Along with many of the Queen Mother's wedding gifts, it was put on public display at St James' Palace, alongside a note from Queen Alexandra, addressed to her ‘dear future granddaughter’. As queen, Elizabeth was not photographed wearing the necklace, but reportedly wore it during a period of courtly mourning for Queen Alexandra.

Queen Camilla, then the Duchess of Cornwall, also wore the piece for an equally grand red carpet moment: the London premiere of Skyfall. Like Catherine, Camilla chose the necklace as a masterly, monochromatic finishing touch to an all-purple ensemble, pairing the pearl-and-amethyst confection with a sumptuous velvet gown.

Buckingham Palace have tended to remain tight-lipped about the specifics of royal wardrobes lately – and Kensington Palace famously stopped reporting on the Princess of Wales ensembles – but could an explanation of this mysterious necklace be incoming?