The King acceded to the throne two years ago, immediately upon the death of the late Queen.
Here are the minute-by-minute developments of the historic day, which marked the end of Elizabeth II’s 70-year reign and the loss of the royal family’s much loved matriarch:
– Thursday September 8 2022: Rumours begin to reach newsrooms early in the morning that the Queen has taken ill at Balmoral Castle, and possibly had a fall.
But she looked frail in photographs and postponed a Privy Council meeting on the Wednesday after being ordered by doctors to rest.
– 10.30am: Behind the scenes, the then-Prince of Wales makes a 120-mile dash by helicopter from Dumfries House to Balmoral after being alerted to the Queen’s worsening condition.
The Duchess of Cornwall cancels a not-yet publicly announced official visit to a cancer centre in Lanarkshire and travels by road from Birkhall.
Charles visits his mother and later goes foraging for mushrooms on the estate as he contemplates his accession and imminent duty as king.
– 12.12pm: Initial indications that something is afoot are seen in the House of Commons.
Then then-chancellor of the Duchy of Lancaster, Nadhim Zahawi, sits down next to PM Liz Truss and begins whispering to her while she listens to Labour leader Sir Keir Starmer’s response to her energy statement.
Sir Keir, too, is passed a note by his deputy Angela Rayner, with Commons Speaker Sir Lindsay Hoyle also being handed a piece of paper updating him about the developing situation.
Ms Rayner later reveals the note read: “The Queen is unwell and Keir needs to leave the Chamber as soon as possible to be briefed.”
– 12.32pm: Buckingham Palace issues a statement, confirming the Queen is under medical supervision.
It reads: “Following further evaluation this morning, the Queen’s doctors are concerned for Her Majesty’s health and have recommended she remain under medical supervision.
“The Queen remains comfortable and at Balmoral.”
Close family have been informed, the Palace says.
– 12.46pm: Clarence House confirms Charles and Camilla have travelled to Balmoral, and a minute later Kensington Palace say William, the then-Duke of Cambridge, is to head north.
The Duchess of Cambridge remains in Windsor where her children, Prince George, Princess Charlotte and Prince Louis are starting at a new school.
– 1.38pm: Palace sources say the Duke of York and the Earl and Countess of Wessex are also on their way to the Queen’s Scottish home.
Harry texts William to ask whether he and Kate are flying up, but receives no reply.
Behind the scenes, Charles calls Harry again to ask him not to bring Meghan.
Charles says only immediate family will be there, and not Kate.
– 2.39pm: A Royal Air Force flight takes off from RAF Northolt in South Ruislip, west London, carrying William, Andrew, Edward and Sophie.
– 3.10pm: Elizabeth II – the nation’s longest reigning monarch – dies at the age of 96 in her bedroom in the castle, with Anne at her bedside. Also there is the Queen’s doctor, GP Douglas Glass.
The Queen’s death – the cause of which is listed on her death certificate as old age – brings an end to the Second Elizabethan age which has spanned 70 years.
He pulls over to take the phone call, confirming the news, in which he is addressed as “Your Majesty” for the first time.
He receives condolences from Camilla, the new Queen, and others accompanying them. He puts the car into gear and continues the drive to Balmoral.
A memo from the late Queen’s private secretary Sir Edward Young records of her final moments: “Very peaceful. In her sleep. Slipped away. Old age. She wouldn’t have been aware of anything. No pain.”
– 3.50pm: The royals on the RAF plane, a Dassault Falcon, land at Aberdeen airport, too late to say their final farewells.
– 4.30pm: Prime Minister Liz Truss is informed of the Queen’s death by Cabinet Secretary Simon Case.
-4.38pm: Sources close to Harry and Meghan say Harry is now travelling alone. He charters a private flight from Luton.
Andrew is in the passenger seat and Edward and Sophie are in the back.
– 5.50pm: A double rainbow appears over Buckingham Palace after a heavy downpour as members of the public gather outside.
A Buckingham Palace statement reads: “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 union flag at Buckingham Palace is lowered to half mast. A death notice is placed on the gates of the Palace as is the custom.
– 7.04pm: Charles issues his first statement as King, and describes his mother’s death as “a moment of the greatest sadness”.
“I know her loss will be deeply felt throughout the country, the Realms and the Commonwealth, and by countless people around the world.”
– 7.07pm: Prime Minister Liz Truss, dressed in black, addresses the nation outside No 10, and confirms Charles will be known as Charles III.
– Around 8pm: Harry arrives at Balmoral. He is in the air when the announcement of the Queen’s death is made.
When he lands at Aberdeen airport, he receives a text from Meghan telling him to call, but learns the news after checking the BBC’s website on his phone.
Charles, William and Camilla – the new Queen – have already left for Birkhall.
Harry visits the late Queen’s body to pay his respects, whispering that he hopes she is happy and “with Grandpa”.
Behind the scenes, the long-held London Bridge plans for the Queen’s death are rapidly put into action, setting out the next 11 days according to a strict timetable which feature a lying in state and then the solemnity and grandeur of a state funeral.
A grieving Charles and Camilla dine with William at Birkhall.
Charles, who has not yet been seen publicly as monarch, and Camilla prepare to return to London on Friday morning, with the King due to address the nation on television.
The King’s historic Accession Council is set for Saturday September 10.