The Strategic Steam Reserve is a rumour, and possible myth. The UK's steam engine reserve during the Cold War.
The place they 'chose' to have it was apparently Tunnel Quarry in Wiltshire, this was used during WWII as a massive ammunition dump. A train would enter through one entrance and a dummy or empty train would leave through the other end, this would fool any German spotter planes above.
Unknown to the enemy, there is a 2 track platform that runs for 200 meters inside the tunnel, this is where they would unload bombs etc onto long conveyor belts that would transport the ordnance to the required area.
Here is a video of how they built the bunker that backs onto the platforms...
(there is a 30 second ad at the start)
http://www.britishpathe.com/video/underground-factories
And in this video (at 2min 13sec) it shows the trains and bomb unloading in use in the tunnel...
http://www.britishpathe.com/video/su...for-our-armies
Back in 2010 explorer's Shadow, Oxygen Thief and Raptor Jesus apparently discovered the SSR with trains fully operational, but that was a hoax.
The platforms are there, but no steam trains to be seen...
Visited with permission of the Ministry of Defence.
1. The walk down to the platform from the main bunker
2. An old mining Loco with mining trucks
3. One of many Conveyor belts that run off the tunnels to storage areas
4. The main walkway tunnel complete with conveyor belt (with belt!)
5.
6.
7. A lift and steps up to the surface
8. Looking up one of the main platforms
9. 100 meters up (half way) PIR sensors trigger emergency lighting, you can see into another section of the tunnel
10. Looking back down the platform, tracks can clearly be seen on the floor
11. A WWII office pokes out of the wall above the conveyor belt
12. Looking back up the platform, you can see the pipes that used to feed the fire hose on the top right of the wall
13. The end of the track.
I have mocked up what it might have looked like during the Cold War...