The UK government’s plan for what will happen in the coming days after the death of Queen Elizabeth II is codenamed “Operation London Bridge”.
It's widely expected to include the period of official mourning and details of her state funeral.
The plans were first created in the 1960s and have been updated throughout each year.
Some critical decisions relating to the plan have been made by the Queen herself, although some can only be made by her successor, Charles, the new King.
The phrase "London Bridge is down" was presumed used to communicate the death of the Queen to the UK Prime Minister and key personnel, setting the next phase of the plan into motion.
The royal family are expected to announce details of the queen’s funeral, which traditionally should be held 10 days following her death.
Parliamentary business is likely to be suspended for 10 days and the sovereign’s coffin is suggested will lie in state for three days at the Houses of Parliament.
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