Buckingham Palace today took the unusual step to announce the Queen has been placed under medical supervision after doctor's voiced concern for Her Majesty's health.
Elizabeth II has reigned for over 70 years and Prince Charles, Camila and Prince William have rushed to Balmoral to be by her side while other members of the royal family have been informed.
The rare statement added that she remains comfortable and is staying at Balmoral.
The 96-year-old monarch celebrated her Platinum Jubilee this year but there have been longstanding concerns over her health and mobility.
And with her husband Prince Philip sadly passing away last year on April 9 2021, and her son Prince Charles taking on more of her duties and reportedly making plans for a "slimmed down" monarchy, thoughts turn to what will happen when the crown passes on.
What happens when the Queen dies?
While there is an element of unpredictability about how the world would react, many elements have been meticulously planned and are likely to bring unprecedented scenes to the UK.
The planning around the Queen's death is known as Operation London Bridge, a hugely detailed plan that will be put into action from the moment she passes away.
Follow the latest updates on the Queen's health today in our live blog
The Prime Minister will be one of the first people to be informed of the monarch's passing. The message will be delivered by the Queen's Private Secretary and sent to members of the Privy Council Office.
From changes to the national anthem, stock market woes and a suspension of comedy shows, here are some of the things we can expect when the Queen dies.
Prince Charles will automatically become King in the event she passes and he will address the nation in a televised broadcast.
The Prime Minister will hold an audience with Charles, while the Ministry of Defence will organise gun salutes and a minute of silence will be held across the country.
Her death would trigger an official 12-day period of national mourning with all Union Jacks flown at half mast.
The BBC will suspend all programming and screen BBC coverage of the event. If Her Majesty dies during the night, her death would reportedly not be announced until 8am.
National mourning
Her Majesty’s death will trigger an official 12-day mourning period for the nation.
Union Jacks will be flown at half mast throughout the country as books of condolence will be opened at embassies across the world.
The London Stock Exchange will be closed for the day of the Queen's funeral as it is expected to be a public holiday. It is not thought that it will be closed at any other stage during the period of mourning.
The Queen’s body will be transported to Parliament, where she will lie in state in Westminster Hall – like the Queen Mother when she passed in 2002 – until her funeral.
It is unknown how many people will travel to pay their respects to the Queen but over 200,000 people travelled to say goodbye to the Queen Mother. The figure is expected to be far higher than that.
Media coverage
The BBC will suspend all of its programming and BBC One will launch coverage of the event.
If Her Majesty dies during the night it is thought her death wil lnot be reported until 8am.
Then her portrait will be displayed on TV along with the national anthem, as happened when Princess Diana tragically died in 1997.
Other channels are not required to interrupt regular scheduling, but it is thought they will.
The BBC will also suspend all comedy programming during the 12-day period of national mourning.
The Beeb regularly rehearses how it will respond to the Queen's death.
The succession
Prince Charles is first in line for the throne and will automatically become King, when Elizabeth II dies.
But the accession council would need to convene at St James’ Palace to formally announce Charles as the king.
He would be asked to swear loyalty to Parliament and the Church of England in front of the council.
Operation London Bridge
There are intricate plans drawn up for the event in which the Queen passes away.
It is codenamed Operation London Bridge but within that are a number of plans that include Operation Unicorn, for if she dies in Scotland, where she currently resides.
It is understood that if Her Majesty dies in Scotland then Parliament, the neighbouring palace of Holyroodhouse and St Giles' Cathedral will be the main focal points for journalists and the public.
It will also mean her body could rest at Holyroodhouse, with her coffin then carried to the cathedral on the Royal Mile.
Her body will then be placed on the Royal Train at Waverley station and a journey down the east coast mainline will commence, finishing in London.
When the Queen passes, the phrase 'London Bridge is down' is expected to be used to communicate the news of her death to key personnel like the PM.
This plan will kickstart the unique media coverage of the event and inform the governments of the 14 other nations of which the Queen remains head of state.
