If you've already spoken to Len, I'll not bother phoning him:)
Interesting about the prints not going down to the adit entrance.
Whatever it is must have got in through the old collapsed pipe vein entrance. It enters the adit above the first flooded shaft (on the RHS as you go inbye) & was very unstable. We brought the worst of the hanging death down a few years back with a couple of gingerly placed "encouragements".
It's still possible there's a critter sized route out to grass through the collapse though.
Not 100% sure where the original entrance was but there's a likely looking spot above & to the right of the current entrance.
I would guess you're interested in the pipe below the main engine shaft. IIRC the last person down there retreated due to poor vis & lots of crap tangled up in there.
Very interested to see what you find.
Nigel
We inhabit an island made of coal, surrounded by a sea full of fish. How can we go wrong.......