The Admirality Citadel. Just because it stuns me that they would build such a thing.→[More:]

It's mentioned quite casually there: you really have to think through the implications.

That WW2 fortress is right in the middle of central London, even then a huge sprawling city of seven million people. For this fortress to come into use, the German Panzer divisions have to have made it past the anti-tank defences on the outskirts, through three concentric rings of defences, fighting street by street through miles and miles of dense suburbs.

By the time they reach the town centre, you would think any commander with a trace of sanity would have evacuated his troops and surrendered the city.

But when Churchill said they would "fight every street of London and devour an invading army" he wasn't kidding or boasting or uttering empty rhetoric. That was the plan. If there's nothing left of unoccupied London but a patch of the city centre, then they were going to stay on that patch and to fight to the death to defend it.

This is madness.
This is London!