She also wore the South-Sea pearl earrings that previously belonged to the Duke’s mother.
The Cambridges have not attended the Berkshire meet for a number of years, partly due to the Covid lockdown, and were cheered by the crowds as they waved from their carriage and at the parade ring.
As the racing got under way, the delighted Duchess appeared to have chosen a Royal Ascot winner, as she grinned at a friend in mock shock after Perfect Power won the Commonwealth Cup.
Earlier in the day, they were photographed in a car at the Long Walk in Windsor, after they were said to have visited the Queen for lunch.
They were joined in their Ascot carriage by friend Arthur Vestey and his wife, Martha.