Queen Elizabeth II's passing marks the end of the longest reign of a British monarch.
While the nation enters a period of mourning for the Queen, who died on 8 September at the age of 96, preparations are under way for the coronation of her son, Charles, as king.
There is no period when there is not a monarch – Charles is already King Charles III –- but there are many formalities to mark the accession.
The Accession Council, a ceremonial body which assembles in St James's Palace upon the death of a monarch, meets within 24 hours of the Queen’s death and proclaims her 73-year-old son king.
The clerk of the council will read the Accession Proclamation, which will then be signed by all the members. Elizabeth II’s saw her commit to defend the faith across Great Britain and Northern Ireland.
What will Charles be known as?
In part two of the Accession Council, Charles will read an oath in front of the members that will include William and Camilla.
It’s at this point that Charles will confirm his regnal name – as some monarchs choose to be known by a different name for the duration of their reign.
His full name is Charles Philip Arthur George, so he could have chosen to use any of those.
Clarence House confirmed hours after the Queen's death that he will be known as King Charles III.
When will Charles' coronation take place?
There’s no set timeline for the coronation of Charles, but the process will be looked after by the Earl Marshal.
The Earl Marshal is a post held by the Duke of Norfolk, currently Edward William Fitzalan-Howard.
He organises the state opening of parliament every year and will oversee the coronation from an office at St James’s Palace.
King George VI was crowned relatively quickly, but that was because his ceremony had actually been organised for his brother before he abdicated.
Queen Elizabeth II acceded to the throne in February 1952, but was not crowned until June 1953.
A delay allows for mourning of the monarch, and also for the extensive preparation of the ceremony.
The coronation has been the same ceremony for about 1,000 years. It will take place in Westminster Abbey, conducted by the Archbishop of Canterbury, and will be watched by other members of the Royal Family as well as heads of the Commonwealth.
Charles will take an oath, be given the crown jewels, and then be invested as king.
He will be crowned with the St Edward's Crown, which is only used for the coronation. Charles won’t even wear it out of the abbey.
Once he is crowned there will be trumpets sounding, bells ringing and a 62-gun salute.
There could be another smaller ceremony for Camilla at the same time, as she becomes the queen consort.
Charles will wear the Imperial State Crown as he leaves the abbey.
The ceremony will likely be broadcast on television and radio around the world. Elizabeth II’s coronation was watched by 27 million people in Britain.
Charles may also follow in his mother and grandfather’s footsteps with an appearance on the Buckingham Palace balcony.
After that, Charles’ work as king begins. His mother toured the country and the Commonwealth in the first few years of her reign.
While Charles is likely to want to visit each nation in the United Kingdom, he has spent decades visiting the Commonwealth and his age could limit the tour in the same way she did it.