Some years back I worked on the redevelopment of The Treasury whist it was on Gordon Browns watch. I had a lot of involvement in the Cabinet war rooms which are underground at the end of the treasury farthest from Whitechapel.
On the outside it is heavily protected by a thick slab of concrete, with about 1.5 metres of it protruding above ground level, reinforced with steel railway lines. Under the actual war rooms are the sleeping quarters for those who worked there, some of the rooms are so small you have to be on hands and knees to crawl into them, no good for a claustrophobe.
These were not accessible to visitors to the war rooms during my time on the project, though I did have the honour of being one of those tasked with taking Lady Soames to reminisce around the project, as it was here that Mr Churchill’s family slept during the blitz.