The Duchess of Cambridge stole the show on Tuesday when she wore one of Princess Diana 's favorite tiaras to the state banquet at Buckingham Palace in honor of King Felipe and Queen Letizia of Spain.

While we're also pretty obsessed with the dusty pink Marchesa dress she wore to the banquet (a version of it is on sale here), we can't take our eyes off of the tiara she picked out for the event.

The Cambridge Lover's Knot tiara was a favorite of the duchess's late mother-in-law, Princess Diana . Commissioned by Queen Mary around 1913 or 1914 from Garrand, a favorite jeweler of the royal family, it is one of the most famous tiaras in the British royal family's collection, according to People. Princess Diana received it as a wedding gift from Queen Elizabeth in 1981, The Telegraph reports.

Princess Diana in the Cambridge Lover's Knot tiara in 1989.

Princess Diana wore the tiara in Italy in 1985.

This wasn't the first time the Duchess of Cambridge channeled her late mother-in-law, nor was it the first time she wore the famous diamond and pearl tiara. Kate wore it to the annual Diplomatic Reception at Buckingham Palace with a red Jenny Packham gown last December.

The first time she wore the famous tiara was at the same event in December 2015 with a white lace dress.

But the Cambridge Lover's Knot wasn't the only royal jewels Kate borrowed for the banquet.

The Duchess looked like a true princess in a bespoke pink Marchesa gown at tonight's state banquet. Unfortunately there aren't many good photos. With a more daring neckline than we are used to seeing Kate in, the dusty pink gown featured very on-trend bell sleeves and an open back with a beautiful full skirt. Kate wore the Cambridge/Queen Mary's Lover's Knot Tiara for the third time tonight. It was commissioned by Queen Mary in 1914. You can read about it's history and see images of the Royal ladies who wore it in the post I did yesterday on the tiaras Kate has worn. Being a piece made famous by Diana, it seemed very appropriate that Kate wear it ahead of the twentieth anniversary of the Princess of Wale's death, as a nod to her late mother-in-law. Kate's earrings were also borrowed from Diana's collection for the first time. These were her Collingwood pearl and diamond earrings that she received as a wedding gift and match perfectly with the tiara. She also borrowed the Queen's King George VI and Queen Elizabeth Bandeau Necklace — a diamond & ruby floral Bandeau collar with a diamond pendant. The Queen received it as a wedding gift from her parents King George VI and Queen Elizabeth. The Queen got much wear out of it during her younger years, but we haven't seen much of it since. ~ There is still no Royal Family Order for Kate—she is the only senior female royal to not have one—but it's not that unusual. The order is an honour given to female royals by the monarch for service to the royal family. Kate will one day receive the Royal Family Order of Queen Elizabeth II, and it is to be worn on formal occasions such as this (in the form of a badge). Because of her family, she hasn't quite committed to full-time royal work, but is starting to do so. This year especially she has put a lot of effort into mental health awareness. Also, she is the Queen's granddaughter-in-law, not married to the Queen's sons like Diana was and now Camilla and Sophie are. Although I'm not sure why Sarah, The Duchess of York was never given one. There's also the fact that the orders are painted in ivory, and Prince William has called for a total ban of its trade in the U.K.

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The diamond and ruby necklace she wore tonight is one that Queen Elizabeth has been photographed in many times over the years.