Up until about 5 years ago, a separate spur off the railway track still existed running on a concrete structure which connected to this series of marshaling lines....
... which converge into 2 tracks which run down a steep incline, then turn a sharp left to rise up and deep into the hill, and this channel has bays either side of it for storage. What did it store? Thousands of tons of bombs on their way to every part of the British Isles, to RAF air bases and from thence to Germany in WW2.
I cannot remember the exact statistics, but I think that about half of all the bombs dropped on Germany from England during the entire war spent some time down this mine shaft - that is a lot of bombs.
There used to be an old man who turned up to my workshop about once a month to spend some time wandering about his old station whilst his wife was having her hair done nearby, and he told me that only one person was killed here during the conflict. That man was changing a light-bulb whilst standing in a pool of water and was electrocuted. I haven't seen the old man for a few years, so I am guessing that he too is now dead.
For years, nobody took any notice of the isolated place aside from industrial archeologists and cave explorers, then the 1980s arrived and the underground network was used for raves and parties. When the party-goers left (or grew up) the place was adorned with the usual graffiti, and this is still refreshed on a regular basis.
Now that the economic crash is occurring and the price of ferrous scrap has rocketed, some desperate and unsavoury characters have been blatantly going down the shaft and pulling out the huge, metal rollers that used to help trundle the 1000 pound bombs into their temporary resting places, and carting them off in an old van to sell to scrap-dealers.
The police know what is going on, but cannot be bothered to do anything about it. When the last bit of 'scrap' has been pulled out, the thieves may turn their attention to the adjacent railway line which is still in use (don't laugh - it happens every day these days). Then the police may have to do something about it, otherwise your trip from London to Bath may be more eventful than you expected.