The King has joined a special lunch for realm prime ministers and governors general at Buckingham Palace.
The Prince and Princess of Wales, the Duke and Duchess of Edinburgh, the Princess Royal and Vice Admiral Sir Tim Laurence were also at the event, which took place 24 hours before the coronation.
Completing the royal contingent were the Duke and Duchess of Gloucester and the Duke of Kent.
There were 42 attendees in total, including UK Prime Minister Rishi Sunak, Australian Prime Minister Anthony Albanese, and Prime Minister of New Zealand Chris Hipkins.
Mr Sunak was laughing and chatting with guests while Kate, wearing a white dress, spoke to leaders including Mr Albanese and Mr Hipkins.
Later, Charles, who is head of the Commonwealth, will also attend a Commonwealth Heads of Government leaders’ meeting and garden reception at Marlborough House.
Some 100 heads of state will descend on London for the King and Queen Consort’s historic coronation on Saturday, with international representatives from 203 countries due to attend.
French President Emmanuel Macron, Germany and Italy’s ceremonial presidents Frank-Walter Steinmeier and Sergio Mattarella and Pakistan’s Prime Minister Shehbaz Sharif will be among those in Westminster Abbey.
Chinese vice-president Han Zheng, who presided over a civil liberties crackdown in Hong Kong, is also on the King’s guest list, but the move has been branded “outrageous” by Conservative MPs.