On Saturday 10th September 2022, the Accession Council will meet to proclaim King Charles III as monarch, following the death of Queen Elizabeth II on Thursday 8th September.
While Charles is already King in title, with his position as the Sovereign becoming set as soon as the Queen passed away, the Proclamation is a constitutional formality and a part of British history most of the UK will have never witnessed in their lifetime.
The Proclamation will officially take place at 10am at St James' Palace in London, with a council proclaiming him King and signing his proclamation before King Charles III enters. The King will then declare his commitment to the UK's constitution and to the Church of Scotland.
The Accession Council will be made up of privy councillors, including Prime Minister Liz Truss, members of her cabinet, members of the shadow cabinet, the Archbishop of Canterbury, the Archbishop of York and representatives of each of the realms of the United Kingdom.
Privy councillors can also include senior civil servants, Commonwealth high commissioners, and the Lord Mayor of London.
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There are more than 700 people who would be entitled to attend the meeting of the Accession Council - however, for King Charles' proclamation the number has been capped to 200 attendees.
The Proclamation will follow King Charles III's first speech, a pre-recorded televised address which was aired at 6pm on Friday 9th September.
How to watch King Charles III's proclamation in historical first
King Charles III's proclamation will take place at 10am BST on Saturday 10th September 2022, and will be broadcast on BBC One, ITV and all major news channels. It will also therefore air live on ITV Hub and BBC iPlayer.
There will likely be a build-up to the event itself, with discussion and news specials airing before the proclamation takes place.
Following the historic proclamation the country will remain in a period of national mourning until after Queen Elizabeth II's state funeral is held.
King Charles III is the oldest monarch to ascend the throne in British history at age 73.
Following the death of his mother Queen Elizabeth II, he said in a statement: "The death of my beloved mother, Her Majesty The Queen, is a moment of the greatest sadness for me and all members of my family.
"We mourn profoundly the passing of a cherished Sovereign and a much-loved mother. I know her loss will be deeply felt throughout the country, the Realms and the Commonwealth, and by countless people around the world.
"During this period of mourning and change, my family and I will be comforted and sustained by our knowledge of the respect and deep affection in which The Queen was so widely held.
"I know her loss will be deeply felt throughout the country, the realms and the Commonwealth, and by countless people around the world."