This post is more of a placeholder/reminder for me; however, I stumbled across some pictures on the Internet of a place called Paddock. This got me searching and I found this Wikipedia article on Paddock and these pictures. Turns out it was an underground bunker that was made for Churchill’s War Cabinet as a refuge of last resort during WW2. It still exists but is privately owned. It also was only used twice for meetings (and those were trial runs). It is open two days per year for the public to view. Paddock’s opening schedule can be found here.
I’m going to try to go next year.
P.S. The image isn’t mine but it is a public domain image I got from wikicommons.