Charles could have chosen to reign under a different name to his birth name, just like many previous kings and queens did.

However, as new Prime Minister Liz Truss delivered a speech from Downing Street, she confirmed His Majesty would be called “King Charles III”.

Truss said: “Today the Crown passes, as it has done for more than a thousand years, to our new monarch, our new head of state, his majesty King Charles III.”

The Prime Minister ended her speech saying “Long Live the King”.

In a solemn message to the nation, Truss said: “Queen Elizabeth II was the rock on which our country was built.

“Britain is the great country it is today because of her.

“She was the very spirit of Great Britain. That spirit will endure.”

It comes on Ms Truss’ third day in office after she met the Queen on Tuesday and was invited to form a Government in her name.

Operation Unicorn is now ready as the country’s longest-reigning monarch dies in her favourite residence, which will likely see the neighbouring palace of Holyrood house and St Giles’ Cathedral as the main places for the public to pay their respects.

According to the plans, during a period of mourning, her body will be moved from Balmoral to Holyrood house in Edinburgh before travelling to London via train.

Buckingham Palace made the announcement at 6.30pm, stating: “The Queen died peacefully at Balmoral this afternoon. The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow.”

The UK is now in a period of official mourning with her funeral due to take place within a fortnight.

The Queen and Prince Philip’s four children – Charles, the Princess Royal, the Duke of York and the Earl of Wessex – were at her bedside, joined by the Duchess of Cornwall and the Countess of Wessex.