The moment the Queen died, the throne passed immediately and without ceremony to the heir, Charles, the former Prince of Wales.
But there are a number of practical – and traditional – steps which he must go through to be crowned King.
What will he be called?
One of his first acts is to decide whether to reign as King Charles III, or take another name.
For instance, his grandfather George VI’s first name was Albert, but he reigned using one of his middle names. Charles could choose from any of his four names – Charles Philip Arthur George.
He is not the only one who faces a change of title.
Although he is heir to the throne, Prince William will not automatically become Prince of Wales. However, he immediately inherits his father’s other title, Duke of Cornwall. His wife Catherine will be known as the Duchess of Cornwall.
There will also be a new title for Charles’ wife, whose full title will be Queen Consort – consort is the term used for the spouse of the monarch.
In the first 24 hours or so after his mother’s death, Charles will be officially proclaimed King. This happens at St James’s Palace in London, in front of a ceremonial body known as the Accession Council.
This is made up of members of the Privy Council – a group of senior MPs, past and present, and peers – as well as some senior civil servants, Commonwealth high commissioners, and the Lord Mayor of London.