The Duchess of Cambridge dazzled at the state banquet for King Willem-Alexander and Queen Maxima of the Netherlands at Buckingham Palace on Tuesday.
Kate has worn the headpiece a number of times including at a diplomatic reception in 2016, and also at a state banquet for King Felipe and Queen Letizia of Spain when they visited Britain past year.
The order, which is also worn by the Duchess of Cornwall, Princess Anne and the Countess of Wessex, features a jewel encased image of the Queen pinned on a chartreuse yellow ribbon and worn on the left shoulder.
Diana also wore it in 1982 at a state banquet for Queen Beatrix of the Netherlands, staged at Hampton Court Palace. People reports that the Lover's Knot tiara is over 100-years-old and belongs to Queen Elizabeth II, although it was originally commissioned in 1914 for Queen Elizabeth's mom, Queen Mary. Her soon to be mother-in-law, Queen Victoria, was still in mourning for her beloved husband, Prince Albert, who had died in December 1861.
A Kensington Palace representative told the Associated Press that there were crowd management concerns, and one royal aid reportedly said the event was "hot, humid and uncomfortably busy and there were far larger crowds than expected".
Diana also wore the tiara in 1985 on an official visit to Washington with Prince Charles.
It was a wedding gift from Queen Victoria's son, the future King Edward VII, to his wife Princess Alexandra of Denmark in 1863.
It's thought that the queen bestowed the order on Kate in December past year.