Kate Middleton is having a princess moment during Buckingham Palace event

King Charles III Attends Reception For Members Of The Diplomatic Corps
King Charles III Attends Reception For Members Of The Diplomatic Corps / Max Mumby/Indigo/GettyImages

After arriving back in the U.K. following a short trip to the United States, Kate Middleton made a ravishing, regal appearance at a Diplomatic Corps reception at Buckingham Palace on Dec. 6. 

For the event -- hosted by King Charles III and Queen Consort Camilla -- the Princess of Wales dressed up in a sparking scarlet, long-sleeve evening gown by Jenny Packham worn with 's Royal Family Order badge and the sash and star of the Royal Victorian Order, which were personal gifts from the late monarch, Queen Elizabeth.

For her jewels, Kate wore several pieces from the royal archives, including diamond frame earrings and diamond Art Deco brooch. She topped off her elegant look with what is known as the Lotus Flower Tiara, sometimes also called the "Papyrus Tiara," which originally belonged to King Charles' grandmother Queen Elizabeth the Queen Mother.

The crown was previously a diamond and pearl necklace, purchased for the queen from Garrard by her husband, later crowned King George VI, as a wedding present in 1923, according to . But the Queen Mother apparently wasn't particularly fond of the design. Less than a year after her royal wedding, she had the necklace transformed into an Art Deco-inspired tiara, featuring scroll and festoon motifs alongside stylized lotus flowers.