After Buckingham Palace announced that doctors are concerned about Queen Elizabeth's health, attention shifted to concerns about the Queen's health and speculations about what will happen if she dies.
 

The "Independent" newspaper mentioned that there has been a wide-ranging plan since the 1960s, called London Bridge is down, under which the Prime Minister is informed who announces the launch of the operation and begins executing the most detailed funeral in the history of the modern United Kingdom.

It explained that there are 48 steps to be taken, including

The Queen’s private secretary, Sir Christopher Geidt, will be the first to learn of the death, and he contacts the Prime Minister to inform him to begin the announcement of the London Bridge is down operation.

Then the Global Response Center of the Foreign Office notifies 15 governments outside the UK where the Queen heads these countries, and 36 other Commonwealth countries, and the Press Union is informed to alert the global media. Then a notice with black borders is hung on the gates of Buckingham Palace.

The British Broadcasting Corporation (BBC) activates the "wireless alert transmission system," which is designated for the death of senior members of the royal family, and media outlets publish their pre-prepared stories, films, and obituaries. The blue mourning lights start flashing at commercial radio stations, and song coordinators switch to the news within minutes. News anchors and broadcasters will wear black clothes and ties. Pilots will announce her death to airline passengers. The London Stock Exchange will also be closed.

If she dies abroad, the royal flight (a BAe 146 from squadron number 32 of the Royal Air Force) will take off from Northolt with the coffin on board.

It was mentioned that the Queen’s coffin will be carried on a green gun carriage accompanied by 138 sailors (a tradition dating back to Queen Victoria) then it goes to Windsor Castle, and when it is brought into the church, the cameras will stop broadcasting, and the country will remain in mourning for at least three days.

The Queen may be buried in St. George's Church in Windsor, Sandringham, or even Balmoral in Scotland.

The Crown Prince Charles, who will become the new king, addresses the nation on the evening of her death, and tickets for his announcement as king will be printed within 24 hours, and Camilla Parker Bowles, Duchess of Cornwall, will become Queen Camilla.

During the nine days following her death, ceremonial announcements and diplomatic gatherings will be held, and King Charles will tour England, Scotland, Wales, and Ireland.

The day of King Charles's coronation will be declared a national holiday, and the words of the national anthem will be changed. There is some confusion about who will become "Head of the Commonwealth," as the title is not hereditary.