On the evening, Kate dazzled in a lengthy Alexander McQueen velvet gown.
The Duchess paired it with a sparkly pair of chandelier earrings and a matching necklace, thought to be items from the Queen’s personal collection of jewelry.
Kate also sported the blue sash of the Dame Grand Cross of the Royal Victorian Order, which is a rank equivalent to a knight.
Eagle-eyed royal fans will also have spotted the Duchess wore the iconic Lover’s Knot Tiara.
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Officially, the tiara belongs to the Queen, who has loaned the gorgeous piece to the Duchess.
The pearl headwear was a favourite of Princess Diana, who was frequently pictured wearing it at formal royal engagements.
The tiara was gifted to the Princess of Wales following her marriage to Prince Charles in 1981.
It is thought the tiara was initially offered to Diana to wear on the big day, however, she chose instead to wear the Spencer family tiara.
The Queen paired the ensemble with white gloves and an emerald necklace.
For her tiara, the Queen chose the Grand Duchess Vladimir Tiara, known for its striking green jewels.
The tiara is thought to be the Queen’s personal favourite of her collection, and was designed by an unknown Russian craftsman.
The tiara consists of fifteen interlaces of thick, metal circles.