Members of the Prime Minister's Cabinet have held an audience with the new King.
Liz Truss took her senior ministers to Buckingham Palace to be received by Charles III for the first time today.
The monarch, 73, who took over from his mum Elizabeth II following her sudden death on Thursday, officially inherited the throne following the Accession Council ceremony this morning.
Ms Truss had met the Queen at Balmoral on Tuesday after taking over No10 from Boris Johnson, 48 hours before she passed away.
For the latest on the royal handover and death of the Queen see our live blog
Charles was introduced to members by the Prime Minister as they lined up inside the 1844 Room at the Palace this afternoon.
He spent time talking to new Foreign Secretary James Cleverly and Defence Secretary Ben Wallace as they flanked the Tory leader.
Earlier, members were present for the formalities of the Accession Council at St James's Palace, televised for the first time.
Charles, 73, automatically became King when his mum died but today's proceedings, in keeping with tradition, saw the council called to make it formal.
Millions of Brits watched the historic moment live for the first time as the medium was in its infancy when the Queen came to power in the 1950s.
In his first statement the King spoke of his mother's "dedication and devotion", adding her death was an irreparable loss.
He said: "My mother’s reign was unequalled in its duration, its dedication and its devotion. Even as we grieve, we give thanks for this most faithful life.
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"I am deeply aware of this great inheritance and of the duties and heavy responsibilities of sovereignty which have now passed to me."
New Queen Consort Camilla was also present at the audiences this afternoon.
She 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.
Following the Cabinet audiences, the King spent time meeting the leaders of opposition parties, including Labour leader Sir Keir Starmer.
Ms Truss had her own first audience alone with the King on Friday following his return to London from Balmoral.
Welcoming her to the Palace, Charles told her the passing of his mother was "the moment I have been dreading".
* This weekend, the Daily Mirror and Sunday Mirror celebrate the life of Her Majesty the Queen with a commemorative special filled with all the key moments from Britain’s longest reigning monarch.
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