The Duke and Duchess of Cambridge attended the annual Diplomatic Reception at Buckingham Palace Tuesday night, and the duchess wore the Cambridge Lover's Knot Tiara, the same tiara that the late Princess Diana used to wear.

Princess Kate arrived at the event with Prince William in a Bentley, with Kate wearing her hair in an up swept style, wore diamond chandelier drop earrings and was dressed in an Alexander McQueen ice blue frock that she wore previously, according to ABC News.

This marks the fourth time that Kate wore a tiara since marrying Prince William back in 2011, but the tiara she wore at the white-tie event was a special once since it was often worn by the late Princess Diana, William's mother.

The tiara was a wedding gift from Queen Elizabeth II, its original owner, to Diana when she married Prince Charles in 1981.

The tiara was returned to the queen's collection after Charles and Diana's divorce in 1996, but she didn't wear it anymore, USA Today reported.

Queen Mary, the present queen's grandmother, commissioned the tiara before the First World War. Underneath each of the 19 lover's knots in the tiara are large natural pearls hanging down, according to Roger Digital Media.