That's the code name given to the plan in place for the days and weeks after Queen Elizabeth II's passing.
The Queen has been sitting on the royal throne since 1952.
That's the longest reign of any monarch in British history.
And during that time, she has seen over a dozen UK prime ministers, nearly 20 Summer Olympics, and over half a dozen popes.
The Queen is the cornerstone to the Commonwealth, the patron to almost 600 organizations and charities, and plays a pivotal role in the UK's alliance with many countries.
So her passing will bring about a lot of change.
Not just for the United Kingdom but potentially the world.
Her private secretary, The Right Honorable Edward Young, will immediately pass a message on to the acting prime minister at the time.
That message will likely read "London Bridge is down."
The prime minister will then set Operation London Bridge into action.
Within minutes, the 15 governments outside of the UK where the Queen is head of state will be informed over a secure line.
And that will be followed by the other 36 Commonwealth nations and leaders around the world.
The gates of Buckingham Palace will then dawn a black-edged notice of the news.
At the same time, a newsflash will alert media around the world.
Every media outlet is prepared for the news.
Every radio station has a network of lights that will flash to indicate a national catastrophe such as this.
All BBC shows will stop and proceed to run a feed dedicated to the news.
Newsreaders will change into the black suits and clothing that is on hand at all times in the news studio, and the traditional red BBC News branding will turn black.
Newspapers, TV channels, and radio stations have days of coverage ready to go.
On the same day as the death, the Queen's eldest son, Charles, will immediately become king.
And it's reported that the stock exchange, businesses, and shops across the UK will likely close for the day out of respect.
The day after the Queen's death, on a livestream, Charles will make his first official speech as King.
And the government will swear its allegiance to the sound of a 41-gun salute in Hyde Park, London.
After that, King Charles, if this is the name he so chooses, will set off on a UK tour, visiting the leaders of government in the capitals of each country, Edinburgh, Belfast, and Cardiff, before returning to London.
During this period, TV channels will play the many documentaries already made in the Queen's honor.
And the BBC will refrain from playing comedy shows as a sign of respect until after the funeral.
Four days after her death, the Queen's coffin will be led on a military procession from Buckingham Palace to Westminster Hall.
Here she will lie in state over the next four days and after which King Charles, family, and dignitaries will pay their respects.
Then, the doors will open to likely hundreds of thousands of people queued up outside.
The funeral is estimated to take place 10 to 12 days after the Queen's passing.
But one thing is certain.
The day of the funeral will be an official bank holiday for the whole of the United Kingdom.
The stock exchange will close for a second time in under two weeks, and many businesses will follow suit.
At 11 a.m. sharp, the bells of Big Ben will chime.
The country will fall silent.
And the coffin will be brought inside Westminster Abbey, where 2,000 specially invited guests will bow their heads in prayer.
After the service, the coffin will be taken to Windsor Castle and then finally to St. George's Chapel, where Queen Elizabeth II will likely be laid to rest next to her father, King George VI.
Likely within a year after the funeral, an official coronation for King Charles will take place on yet another bank holiday.
All in all, accounting for the multiple bank holidays, funeral expenses, and coronation celebrations, the Queen's passing is estimated to cost the UK economy billions of pounds.
In addition, hundreds of changes will happen across the UK in the months to come.
New British currency will be printed with the King's portrait, and the Queen's currency will slowly be removed from use.
The same will happen for stamps, passports, and police and military uniforms.
And the national anthem will be changed to "God Save the King."
Not to mention, how the world and Commonwealth will react to the new King could alter the British royal family forever.
For example, there is growing support in Australia for the country to become a republic.
And the Queen's death could heighten that support.
This could lead other countries to follow suit, which would almost certainly weaken the British monarchy.
This scenario will one day be upon us.
Operation London Bridge will be triggered, and arguably the biggest funeral of our lifetime will be witnessed around the world.