Despite the fact the Queen is currently alive and well, a meticulous plan has already been laid out for her death.

A code word has already been decided upon to deliver the news of her passing to the highest tiers of government.

While the death of George VI was signalled by the words “Hyde Park Corner” - to stop switchboard operators at Buckingham Palace learning the news - the equivalent word for Queen Elizabeth II is “London Bridge is down”.

According to The Guardian, the Prime Minister at the time will be woken, if not already awake, and informed by civil servants that “London Bridge is down”.

These words will signify the monarch has passed away and kick off Operation London Bridge – a highly-organised set of arrangements which will eventually culminate in the Queen’s funeral.

Queen Elizabeth II: Britain’s longest-reigning monarch

The Foreign Office’s Global Response Centre, located at an undisclosed location in London, will then immediately inform 15 governments outside the UK where the Queen is also the head of state. After this, the centre will pass on the news to the 36 other nations of the Commonwealth for whom the Queen has served as a symbolic figurehead for many decades.

It will not be long before the news spreads from world leaders to the general public, with the news of her passing released as a newsflash to the Press Association and thus the global media simultaneously.

This marks a break from the long-held tradition of the BBC being the first news outlet to learn of royal deaths. What’s more, while George VI’s death was not announced until four hours after he died, news of the Queen’s demise will be far more instant.

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A footman in mourning clothes will be sent out of the door at Buckingham Palace at the same time to pin a notice of the news to the gates, while the official palace website will feature just one page, revealing the news on a dark background.

Coverage of the Queen's passing will kick off immediately. Newspapers and online media outlets already have news stories about her death and lengthy obituaries and supplements ready to publish at a moment's notice. At the BBC, the “radio alert transmission system” will be activated and rehearsals for the Queen’s death will be put into action.

Sky News and ITN, which have reportedly spent years rehearsing the death of the Queen by substituting the monarch's name for “Mrs Robinson”, will contact royal experts who have already signed contracts to speak exclusively to them.

British commercial radio stations will switch on blue “obit lights” to alert DJs to switch to the news imminently and play inoffensive music in the lead-up.

In turn, carefully prepared coverage of the longest-reigning monarch, who recently announced she would step down as patron of a number of organisations and charities before her 91st birthday in April, will dominate the news for weeks and months.