The King has arrived at Buckingham Palace, where he will meet with Commonwealth general secretary Patricia Scotland.
Crowds lining the roads cheered and waved as his black car drove down The Mall and into the Palace gates accompanied by a motorcade of four cars and four police motorbikes.
Charles could be seen waving to people through the car windows.
Children sat on top of parents’ shoulders and people took photos as they watched the new sovereign arrive.
King Charles III arrives at Buckingham Palace
Ian West
Earlier on Sunday, Buckingham Palace said the King would hold audiences and a reception later in the day.
At 2pm, Charles receives the Secretary General of the Commonwealth in the 1844 Room at the Palace.
At 2.30pm, he will attends a reception with Realm High Commissioners in the Palace’s Bow Room.
At 3.30pm, the King receives the Dean of Windsor in the 1844 Room.
Guests will include Foreign Secretary James Cleverly and High Commissioners for Antigua and Barbuda, Bahamas, Belize, Canada, Grenada, New Zealand, St Christopher and Nevis, St Lucia and St Vincent and the Grenadines, and the Honorary Consul of Tuvalu and the Acting High Commissioner for Australia.
It comes as Queen Elizabeth II's coffin is travelling from Balmoral to Edinburgh.
The coffin is expected to arrive into the Palace of Hoylroodhouse later today, where it will remain for the night.
The King waved to crowds waiting outside Buckingham Palace
HENRY NICHOLLS