Here is how the day unfolded.
Buckingham Palace issue a statement saying doctors are concerned for the Queen’s health.
They say the head of state is comfortable and royal physicians have recommended she stays under medical supervision as the future king, the Prince of Wales, and second in line to the throne, the Duke of Cambridge, clear their diaries to dash to the Queen’s Aberdeenshire home.
Clarence House said Charles and the Duchess of Cornwall have travelled to Balmoral.
A minute later Kensington Palace confirmed William would also be travelling north.
Royal Air Force flight KRF23R takes off from RAF Northolt in South Ruislip, west London, according to flight tracking website Flightradar24.com.
The plane is carrying William, the Duke of York, and the Earl and Countess of Wessex.
The plane, a Dassault Falcon, lands at Aberdeen airport.
– Just after 5pm
A fleet of cars, including a Range Rover driven by William, with Andrew in the passenger seat and Edward and Sophie in the back, arrives at Balmoral.
Buckingham Palace say in a statement: “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.”
– Just after 7pm
Charles, who became King on the death of his mother, said: “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.”
Prime Minister Liz Truss said it was “the passing of the second Elizabethan age” and concluded an address by saying “God save the King”.
She refers to Charles, the new King, as King Charles III, saying: “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.”
Clarence House confirms that Charles will be known as King Charles III.