But one of Kate's accessories appeared to hint at a big change for the future.
Kate displayed her Royal Family Order, as is custom for formal occasions such as the Diplomatic Reception or state visits.
The miniature depicts Queen Elizabeth II and is attached to a yellow silk ribbon, but it has been noticeably shortened since the South Korean state banquet last month.
Queen Camilla also sported a shortened ribbon with her Royal Family Order.
HELLO!'s Royal Editor Emily Nash shares some insight into what it could mean: "The King will issue his own Royal Family Order in future, which will replace the one worn by Queen Camilla and Princess Kate, and the shorter ribbon displayed is a reminder of that coming change.
"I would expect to see them wearing the King's portrait this time next year."
The late Princess Margaret often displayed her three Royal Family Orders – King George V, King George VI and Queen Elizabeth II.
Kate became the first British royal to wear a Royal Family Order made with glass instead of traditional ivory when she was awarded it in 2017.
This is believed to be because of William's work around conservation and his commitment to end the ivory trade.
The future king set up the United for Wildlife (UfW) umbrella organisation in 2014 to tackle the illegal trade in animal products.
The miniature of Queen Elizabeth II on glass is bordered by diamonds and surmounted by a Tudor Crown in diamonds and red enamel. The reverse, in silver-gilt, is patterned with rays and depicts the royal cypher and St Edward's Crown in gold and enamel.
Kate also displayed her Royal Victorian Order and blue sash at the Diplomatic reception. The Princess was appointed a Dame Grand Cross of the Royal Victorian Order (GCVO) by the late Queen for services to the sovereign on her eighth wedding anniversary in 2019.
Queen Camilla and Prince William both wore their Garter sash and star to the palace reception.
Kate is not part of the Order of the Garter but she has joined her husband at the annual ceremony since his induction as the 1,000th Knight in 2008.
It was one of the first major royal events Kate attended before her marriage to William.
LISTEN: How Prince William supported Kate when she joined the royal family