This is a very long tunnel, over 2000 yards, built during the Second World War to transport munitions from a railway siding to ammunition stores in nearby Monkton Farleigh mine.
It used a short rope hauled railway to move goods from the siding down into the tunnel, and then a series of conveyor belts. It has a nice underground marshalling yard with offices.
We didn't explore the whole length of the tunnel due to time and because of it being a bit long and boring!
Pics aren't great (I'm not much of a photographer) but hope you enjoy anyway.
The entrance building - as you can see it's just a cut and cover tunnel.
A pillbox nearby
Winding gear inside the entrance building - this was in a room down a ladder.
Looking down into the tunnel
Underground offices
Electrics box
Office again
Underground marshalling yard for light railway
In the tunnel - remains of the conveyor belt
Looking up the tunnel from the offices - it curves round before it goes outside
Looking up outside