Queen Elizabeth, Britain's longest-reigning monarch, and the nation's figurehead for seven decades has died aged 96, Buckingham Palace said on Thursday.
"The Queen died peacefully at Balmoral this afternoon," Buckingham Palace said in a statement. "The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow."
Her eldest son Charles, 73, automatically becomes king of the United Kingdom and the head of state of 14 other realms including Australia, Canada, and New Zealand.
"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," Charles was quoted as saying in a statement issued by the Royal Family.
"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," he added.
Her family had rushed to be by her side at her Scottish home, Balmoral Castle, after doctors expressed concern about her health. She had been suffering from what Buckingham Palace has called "episodic mobility problems" since the end of last year, forcing her to withdraw from nearly all her public engagements.
Upon the Queen's passing, the United Kingdom — where she reigned for a record 70 years — was plunged into public mourning.
Plans for the Queen's death and the accession of Charles, 73, to the British throne are code named Operation London Bridge and Operation Spring Tide respectively. The plans provide details from the "London bridge is down" code used to convey news of the monarch's passing to the Prime Minister, to design changes to government websites to mark the occasion. If the Queen dies in Balmoral — as she has — another set of steps called 'Operation Unicorn' is triggered, according to a 2021 report from Politico.
Her body, as per this protocol, is to be brought to London by train or by plane and will be received by Ms. Truss in London. The Prime Minister and the new King are expected to make a statement on Thursday. The funeral, if the reported protocol is followed, is expected to be held on the tenth day following the Queen's death.
According to news agency AFP, the Queen pulled out of a planned meeting with her senior political advisors on Wednesday, after being told to rest. The previous day she had audiences at Balmoral - her Scottish Highlands retreat, with outgoing Prime Minister Boris Johnson and appointed his successor, Liz Truss.
In recent months, the Queen appeared visibly frail and had a series of withdrawals from public engagements. She had taken to walking with a stick and was also seen touring the Chelsea Flower Show in a motorized buggy.
In June, the UK came together for the Platinum Jubilee celebrations to mark the 70th anniversary of the Queen's accession to the British throne. Her husband, Prince Phillip, died last year at the age of 99, two months before his 100th birthday.