The business of monarchy continued as usual on the day Liz Truss resigned, with the King holding meetings at Buckingham Palace.
Ms Truss said she had spoken to Charles and notified him that she is resigning as leader of the Conservative Party, but she will still have to meet him in person to formally tender her resignation, as is tradition.
This will take place immediately before the monarch asks her successor, also in person, to form a government.
On Thursday, Charles held the first credentials presentations of his reign.
He met Ukrainian ambassador to the UK Vadym Prystaiko and high commissioner of Pakistan to the UK Moazzam Ahmad Khan.
The presentations took place in the 1844 Room at Buckingham Palace.
In these ceremonies, a newly appointed ambassador or high commissioner to the Court of St James’s presents their letters of credence or high commission – known as credentials – to the monarch.
Credentials presentations take place when a mutually convenient date is found after an ambassador or high commissioner take up their post.
Charles also held an audience with the president of the Togolese Republic, Faure Gnassingbe.
It is not known when exactly Charles spoke to Ms Truss on Thursday.
He held his weekly audience with her on Wednesday evening at the palace, according to the court circular.
When the King held his first weekly audience with Ms Truss on October 13, he welcomed her to the Palace by saying: “Back again? Dear oh dear.”
Ms Truss replied: “It’s great pleasure.”
Charles as sovereign plays an important constitutional role in the appointment of a new prime minister.
The Royal Encyclopedia states that the appointment of a prime minister is “one of the few remaining personal prerogatives of the sovereign”.
It says that, in the normal course of events, the monarch does not act on advice nor need to consult anyone before calling upon the leader with an overall majority of seats in the House of Commons to form a government.
But the monarch is guided by constitutional conventions and can seek advice from the outgoing prime minister, any other political leader, senior privy counsellors, or whomever they please within the limits of prudence and caution.
Meanwhile, credentials are part of the King’s work on behalf of the Foreign, Commonwealth and Development Office.
The letters are addressed to the King, asking him to give “credence” to the new ambassador or high commissioner – in other words confirming that the King can trust the new appointment to speak on behalf of their country.
Credentials typically take place on a regular basis, as there are more than 170 ambassadors and high commissioners based in London at any given time, and each one of them will have an audience with the King shortly after taking up the role.
They will often bring members of their family to the occasion.
After the presentation of the credentials, the King and the visiting party will then speak informally for the rest of the audience.
Often the emphasis is on issues of the day in the home country of the ambassador or high commissioner.
In March, the King and Queen Consort – then the Prince of Wales and Duchess of Cornwall – lit candles and left floral tributes at the Ukrainian Catholic Cathedral in London as they acknowledged the plight of the eastern European nation.
They were joined by Mr Prystaiko and his wife Inna Prystaiko.
On Monday of this week, Charles welcomed refugees from Ukraine, Syria and Afghanistan as he learned of efforts to resettle displaced families in Aberdeen.
In a reception at the city’s Town House, the King met Inna Skvortsova, a Ukrainian woman who arrived in the city in April.
She now has a full-time role at the council assisting with the resettlement programme.
In August it was revealed that Charles would make a donation to aid charity Islamic Relief to help those affected by the floods in Pakistan, which he said “remind us of the fragility of our planet”.
He also sent a message to the government of Pakistan in which he said: “Times like these remind us of the fragility of our planet and the urgent need for humanity to live in harmony with nature.”
