King Charles III formally proclaimed Britain’s new monarch in centuries-old Accession Council ceremony

King Charles III, the world’s newest monarch, was officially proclaimed sovereign of the United Kingdom of Great Britain and Northern Ireland on Saturday morning in a constitutional ceremony that dates back hundreds of years. Almost 700 members of the current Accession Council, the oldest functioning part of Britain’s government, were called to convene Saturday at St James’s Palace in London, the official residence of the U.K.’s kings and queens for centuries.

For the first time in the Accession Council’s long history, the two-part ceremony is being aired on television Saturday. You will be able to watch the proceedings live on CBS News, in the player above.

The council is comprised of Privy Counsellors, a select group of senior politicians, including new Prime Minister Liz Truss, religious figures from the Church of England, the Lord Mayor of London and a bevy of other top civil servants from across British society and the 14 other “realms,” or nations, for which the monarch serves as the official head of state.

While King Charles III immediately became the king upon the death of his mother, Queen Elizabeth II, who died Thursday after a record 70 years on the throne, it was the council’s role to formally acknowledge the passing of one monarch and to then proclaim the new one on behalf of the British government. It is part of Britain’s constitutional process.

Around 200 of the current Privy Counsellors attended the proceedings in London on Saturday, including many former prime ministers and other senior politicians. The Privy Council is the oldest functioning part of Britain’s government, dating back almost 1,000 years.

In the first part of the ceremony, British lawmaker Penny Mordaunt, the Lord President of the council, announced the death of Queen Elizabeth II and then clerk of the council, Richard Tilbrook, read out loud a proclamation of accession.

The proclamation was then signed by members of the council.

For the second part of the council, King Charles joined the gathering at St James’s. The Privy Counsellors watched as the new monarch read out declarations relating to his mother’s death, and then swore an oath vowing to serve the Church of Scotland, of which he is also the formal leader. 

The king was then first to sign two copies of the declaration, followed by his son and heir, William, Prince of Wales, and other witnesses. 

Following the Accession Council proceedings, the proclamation of King Charles as the monarch was read out loud from the Proclamation Gallery, a balcony of St James’s Palace, by the Garter King of Arms, accompanied by other officials — all wearing traditional clothing. 

Trumpets blared as the Garter King of Arms prepared to read the proclamation. Afterward, another trumpet salute followed a cry of “God save the king!” by those gathered in the courtyard under the Proclamation Gallery. The assembled crowed then sang the British national anthem, with its newly revised lyrics of “God save the king.” 

The proclamation was to be followed by gun salutes, before the proclamation was repeated at other locations in London and then in the capital cities of the United Kingdom’s other home nations, in Edinburgh, Scotland; Belfast, Northern Ireland, and Cardiff, Wales, among other locations.

The rest of King Charles’ third day on the job will involve a range of formal meetings — or “audiences,” as they’re referred to by Buckingham Palace — with officials including the Archbishop of Canterbury, the prime minister and other members of the cabinet, and then leaders of Britain’s political opposition parties.