The King and Queen shook hands with members of the public as they returned to their official London residence after Charles held audiences at Buckingham Palace.
Charles was joined by Camilla on Stable Yard, off The Mall, outside Clarence House where they interacted with well-wishers on Saturday.
Cheers and applause rang out as they shook hands and accepted bouquets of flowers from people who had waited for hours.
Shouts of “God save the King” were heard along with a chorus of the national anthem.
Alex Dellipiani was celebrating her 16th birthday when she met the Queen Consort.
She said: “She asked, ‘How old are you?’ I said, ‘16’ and she said, ‘You’re very lucky’.
“It was a once-in-a-lifetime opportunity.
“We have been standing here so long and it was amazing.”
The pair greeted the crowds as the King arrived in a Rolls Royce, having left the palace where he had been meeting politicians earlier in the afternoon.
Charles had an audience with Liz Truss, who brought her senior ministers to the Palace to be received by the sovereign for the first time.
Camilla was also present at the audiences and chatted to Cabinet members including Leader of the House of Commons Penny Mordaunt, who oversaw the Accession Council in her role as Lord President of the Council.
The meetings followed the accession proclamation, made to a crowd from the balcony of St James’s Palace.