It's strange how often one comes across a small hillside cave that has a locked grille-gate to it.
I have never quite figured out what's going on though. My first guess is that someone found the cave and thought it might be a useful storage area or temporary animal pen - especially as they are often in remoter areas - so they put in a secure gate and a lintel to hold it in place.
One shudders to think that it might have been used as a prison/lock-up for humans.
But I really don't know.
This one is on the road at Dale Bridge near Wetton.