Kate Middleton has always has an eye for fashion. She has long been a style icon, having influenced both the British and American fashion industry, so much so that she even has her own "effect" named after her. From bridal wear to jeans, she has always dressed with flair.

But perhaps her most stunning look to date was seen at the Buckingham Palace recently, where the Queen's annual diplomatic reception was held.

According to the Daily Mail, "It is certainly the largest reception held annually at Buckingham Palace, with more than 1,500 dignitaries invited from around 130 countries, including members of the British government, past Prime Ministers, the Archbishops of Canterbury and York and other public figures."

The Duchess of Cambridge looked radiant at the back of a Bentley, with a tiara perched on her made-up locks. But this was no ordinary tiara, it was the Cambridge Lover's Knot tiara, the very one Princess Diana had previously owned.

The diamond and pearl head piece was originally made by Queen Mary in 1914. She had designed the tiara and made it from the diamonds and pearls that her family already had.

Princess Diana had received the shimmering tiara in 1981 as a wedding gift. She wore it at the state opening of parliament for the very first time and dazzled everyone. Four years later, she wore it again while on an official visit to Washington with her husband, Prince Charles.

Prince William's beautiful wife has only worn tiaras three times before. The first time was at her wedding in 2011, where she donned a brilliant Cartier tiara. The second time was at the Queen's 2013 diplomatic reception. And the third time was in October at the state banquet held at Buckingham Palace. For her second and third times, the mother of two wore the Lotus Flower tiara, which reportedly the Queen Mother once possessed.

It is unknown whether the Duchess of Cambridge received the Lover's Knot tiara as a gift or whether she was simply borrowing it for the night's event.