Kate was also wearing the royal family order just below her left shoulder — a personal gift from the Queen to female members of the royal family.
The duchess first wore it at the diplomatic reception before Christmas, but it likely wasn’t seen as just car shots were taken publicly.
The order takes the form of a picture of the Queen — and in Kate’s case it is on glass. Previously, they have been made with ivory, but in keeping with William and Kate’s shared hope to halt the use of wild animal parts, Kate’s was made with glass.
The Dutch royals, who are on a two-day State Visit to the UK, appeared in excellent spirits as they posed for photos with the Queen, Prince Charles, and the Duchess of Cornwall, before taking their seats in the opulent dining room.
All eyes were on the Duchess of Cambridge's tiara.
The Cambridge Lover's Knot, once owned by the Princess of Wales, was made by Royal jewellers Garrard in 1914 to Queen Mary's personal design, from pearls and diamonds already in her family's possession.
It was a copy of one owned by her grandmother, Princess Augusta of Hesse, who married the first Duke of Cambridge, seventh son of King George III, in 1818.
In her will Queen Mary left the tiara to to the Queen who wore it frequently, including at an evening event in 1955.
In 1981 she gave it as a wedding present to Prince William's mother, Diana, who wore it for the first time at the state opening of parliament that November.