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Kate Middleton, Duchess of Cambridge, stunned Thursday evening at a diplomatic reception at Buckingham Palace.

Kate wore a red Jenny Packham gown along with a regal tiara that once belonged to her late mother-in-law, Princess Diana.

The Cambridge Lover’s Knot tiara was made in 1913 at the request of Queen Mary, according to the Telegraph. Mary left the tiara to Queen Elizabeth II, who gave it to Princess Diana as a wedding gift.

According to the Today Show, the crown is reportedly so heavy that it gave Princess Diana headaches.

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