As the Princess of Wales, Catherine is afforded a number of privileges, including access to jewels from the royal vault.
One of these is a historic diamond and emerald feather brooch, which is specifically reserved for the wife of the Prince of Wales. Prince William's wife exercised her right as she welcomed the Sultan of Oman for his state visit.
Joining King Charles and Queen Camilla on the Royal Dais in Datchet Road, Catherine was the epitome of elegance in a bottle-green Sarah Burton for Alexander McQueen coat with a belted waist, which she recycled from her sustainable wardrobe.
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The royal first wore the structured midi jacket during her Boston tour in late 2022, and again for St. Patrick’s Day in 2025. She completed her look with a black lace top, which was visible above her lapels, a matching green Juliette Botterill hat and her sparkling Prince of Wales Feather Brooch.
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The 160-year royal protocol behind Princess Catherine's exclusive heirloom
The accessory, which featured a detachable cabochon emerald pendant, was originally a wedding gift to Princess Alexandra of Denmark when she married the Prince of Wales in 1863. It was then passed down to the Queen Mother, who gifted it to Princess Diana to mark her engagement to then-Prince Charles in 1981.
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Catherine's mother-in-law wore it as a pendant on a diamond necklace from 1982 to 1996, according to the Royal Watcher. It seems it was returned to Charles after Diana's death, as his second wife, Queen Camilla, was later spotted wearing the diamond and emerald piece in brooch form for the film premiere of The History Boys in 2006. It went on to become a staple in her wardrobe for events such as Cheltenham and Ascot.
After the late Queen Elizabeth II died in 2022 and she was bestowed the Wales title, Catherine debuted the brooch for the South African State Visit in 2022.
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Sultan of Oman's state visit
Shortly before their outing, Prince William was seen chatting with Sultan Haitham bin Tarik at the Sultan's residence, as he welcomed him on behalf of King Charles. They then posed for an official photograph and shook hands before travelling to meet the King and Queen.
Charles then rode in the Irish State Coach with Sultan Haitham bin Tarik, while Queen Camilla followed in the Scottish State Coach with Sayyid Shihab bin Tariq Al Said, Oman’s deputy Prime Minister for Defence Affairs.
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The Prince and Princess travelled in the Australian State Coach with Sayyid Theyazin bin Haitham Al Said, deputy Prime Minister for Economic Affairs and Sayyid Loay bin Ghalib Al Said, Secretary General of the Diwan of the Royal Court.
The royals are expected to gather for a state banquet this evening at Windsor Castle, which will see another glittering display of diplomatic dressing.
Other visiting officials followed in two Ascot Landaus as the procession made its way through Windsor town centre and through the Cambridge Gate into the Castle.