Caradon used to be open and was fitted with a big metal trap door by some local mineral enthusiasts who had permission. (early 90's? )
This lapsed and in the meantime, the trap door (which is of huge construction) rusted solid. The lock is also inaccessible and is rusted solid.
Kenneth Brown and Bob Acton talked about an adit collapse. People had used this to bypass the trap door. This has subsequently totally collapsed and is utterly inaccessible.
A local group was looking into getting permission to go underground there, but I gather it is a non-starter due to the collapses and the amount of digging required.
There is no access there nor is there likely to be any at any point in the future, unless Pearce's Shaft opens up.
To the best of my knowledge, the last people in there were the minerals lot who may or may not be poking around.
Edit:- Also, it is very likely that the adit collapse has also blocked off the trap door access tunnel. Rotten granite.