Getty Images; Samantha Lee/Business Insider
Queen Elizabeth the Second, by the Grace of God Queen of this Realm and of Her other Realms and Territories, Head of the Commonwealth, Defender of the Faith, is not going to live forever.
Since ascending to the throne in 1952, the monarch has seen 13 Prime Ministers serve Britain, and lived through another 13 US presidents. She's now 92. At some point - not for many years yet, we hope - Queen Elizabeth II's reign will come to an end.
But what happens then?
For at least 12 days - between her passing, the funeral and beyond - Britain will grind to a halt. It'll cost the UK economy billions in lost earnings due to the chaos. The stock markets and banks will likely close. And both the funeral and the subsequent coronation will become formal national holidays, each with an estimated economic hit to GDP of between £1.2 and £6 billion, to say nothing of organisational costs.
But to focus on the financial disruption doesn't begin to describe the sheer magnitude of it. It will be an event unlike anything Britain has seen since the end of the Second World War.
There will be trivial disruptions - the BBC will cancel all comedy shows, for example - and jarring cultural changes. Prince Charles may change his name, for instance, and the words of the national anthem will be changed, too. The British Commonwealth might even unravel completely.
The deaths of Princess Diana and the Queen Mother both brought on waves of public mourning and hysteria. But the Queen, due to her longevity and fundamental place atop British society, will be on a whole new level above that.
The vast majority of British people have simply never known life without the Queen.
It will be a strange, uncertain time.