Kate Middleton Has Major Princess Moment in Diamond Tiara That Hasn't Been Worn Since the 1930s

The Princess of Wales helped King Charles host the President of the Republic of Korea, Yoon Suk Yeol, during a state visit to the U.K.

Kate Middleton just added another glamorous tiara to her fashion history.

The Princess of Wales, 41, attended a state banquet at Buckingham Palace on Tuesday evening, part of the state visit hosting the President of the Republic of Korea Yoon Suk Yeo and First Lady Kim Keon Hee. She joined King Charles, Queen Camilla, Prince William, other members of the royal family and around 170 guests at the white-tie event.

In a surprise style moment, Princess Kate wore a tiara she had never worn before — the Strathmore Rose tiara. The debut marks the fourth tiara worn by the Princess of Wales during her royal life.

The floral headpiece had not been seen in nearly nine decades (since the 1930s!) but was part of the Queen Mother's collection. According to The Court Jeweller, the accessory's name comes from the Queen Mother's father, who was the Earl of Strathmore and Kinghorne, and was a wedding present when she married Prince Albert (the future King George VI, Queen Elizabeth's father).

Following the Queen Mother, Princess Kate is only the second person to wear the Strathmore Rose tiara in public.

Related: Every Time Kate Middleton Has Worn a Tiara — See the Photos!

"Kate has always signaled that she'd like to emulate the Queen Mother's royal role, and wearing her jewels is an important symbol of that continuity," Lauren Kiehna, founder of The Court Jeweller, tells PEOPLE. "It's fitting that Kate—likely with some assistance from King Charles—would choose to wear the tiara exactly a hundred years after the Queen Mother originally received it. The piece is an antique that wasn't fashionable for many decades, but many jewels once considered fussy or unstylish have now been embraced again."

"The tiara comes with two frames, allowing it to be worn either across the forehead or on top of the head. The Queen Mother used it both ways, and Kate chose the more traditional setting for the banquet," adds Kiehna.

King Charles was famously close to his grandmother, who died in 2002, and Princess Kate bringing the tiara back into the public eye is likely a nod to her bond with the monarch. Just recently, the King referred to Kate as "my beloved daughter-in-law."

For Tuesday night's banquet, Princess Kate wore a white Jenny Packham dress with gold embellishments, earrings that belonged to Queen Elizabeth and her honors: the Royal Family Order and her Grand Cross of the Royal Victorian Order sash and star.

Princess Kate has previously worn three different royal tiaras, starting with her wedding day in April 2011 when she sported the Cartier Halo tiara.

She made her debut in the Lotus Flower tiara at a diplomatic reception at Buckingham Palace in 2013. Kate opted for the same headpiece in 2015 while welcoming Chinese President Xi Jinping to the palace, then went seven years before reaching for the Lotus Flower again for the 2022 Diplomatic Corps reception.

Princess Kate's go-to headpiece for such occasions is the Queen Mary's Lover's Knot tiara, featuring elegant lover's knots and hanging pearls. Since wearing it for the first time in 2015, she has worn the accessory 11 times. The piece was a favorite of her late mother-in-law Princess Diana, who wore it on multiple occasions. According to the Court Jeweller, the stunning sparkler is more than a century old and was originally commissioned from the jeweler Garrard by Queen Mary in either 1913 or 1914. It is a replica of a tiara owned by Mary's grandmother, Princess Augusta of Hesse, the Duchess of Cambridge.

Related: Kate Middleton Drops into an Expert Curtsy for King Charles — While Navigating Stairs!

Princess Kate's last tiara wear came in June at Crown Prince Hussein and Princess Rajwa of Jordan's royal wedding banquet. Although it's a familiar look for the royal, Kate also wore the Queen Mary's Lover's Knot differently than usual at the event. While she typically wears her hair in an elegant updo for formal occasions calling for royal head-toppers, the princess opted to wear her hair down at the wedding banquet.

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At Tuesday evening's banquet, King Charles gave a speech starting with a line delivered in Korean welcoming their guests to Britain, which was met with applause.

In addition to praising the nation's efforts on sustainability — with a special shout out to K-pop band BLACKPINK, who attended the banquet — the monarch referenced Korea's influence on pop culture rivaling the U.K.'s! "Korea has matched Danny Boyle with Bong Joon-ho, James Bond with Squid Game and the Beatles' 'Let It Be' with BTS’s 'Dynamite,' " he said. "Our cultures share a remarkable ability to captivate imaginations across the world, transforming a so-called soft power into a shared superpower."

While most glasses at Tuesday night's banquet continued to feature the late Queen Elizabeth's cypher, the head table at the event featured glasses etched with King Charles' royal cypher for the first time.

Princess Kate and Prince William greeted President Yoon Suk Yeol and the first lady at their hotel on behalf of King Charles on Tuesday morning before traveling to Horse Guards Parade for a ceremonial welcome.

In the days after Queen Elizabeth's death in Sept. 2022, King Charles made William and Kate the new Prince and Princess of Wales, recognizing their seniority in the family and signaling their critical roles ahead.

“Charles is leading the way for them already, and [William and Kate] are both involved in decision-making behind the scenes. They are ready and willing to do the job — and Kate is very much a part of that,” a friend of the princess recently told PEOPLE.

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