I actually blundered into 10 gp operations room in the tunnels around RAF Rudloe Manor at Box in Wiltshire in the 80's while serving on security duties in the RAF communication centre during the cold war. Massive tunnels built before ww2 around Corsham in Wiltshire up to RAF Colerne, the RAF still had a major underground comms centre known as 6su then with the hq of Defence communications based there in the tunnels. All new stuff by then, but the old tunnels stretched for miles, and were still lit up. Mostly used for storing ammo in ww2 and rail tracks and platforms still around, old teleprinter rooms, posters on walls, kilroy was here etc, stretching to a secret entrance at BOX tunnel where ammo trains were despatched into the complex on a seperate gauge and line.
Massive complex, with big underwater lake fenced off. One night when bored 3 of us got lost with torches, and blundering around one of the complexes, which even then were to be the bolt hold supposedly for govt and royals, we entered a gated area and shone our torches on hq 10 group, the shape and design not much different from movies and area shown in RAF museum for 11 gp, brilliant stuff, the plotting table still central, nothing on it of course, and alcoves above where controllers must have directed it, history exists still, underground Britain, sadly though I believe this lot has now been destroyed, certainly although RAF still there and Army, most of the tunnels have been purpolsely caved in.
A haunt of UFO believers, who beleived because there was a low flying police cell based at Rudloe Manor that they also investigated UFO's sadly not true, I was there, we just took reports of low flying aircraft complaints for MOD policing and service police, which by nature included all reports of low flying ufo's be they real or imaganery, but ufologists then thought we were hiding something.

Fascinating place.