Just for the sake of reporting progress...
Myself and a work colleague thought we'd have a closer look at this collapsed level last night.
I was astounded, and rather pleased, to discover that with lots of slithering and climbing and generally hoping for the best, it was possible to worm our way through the collapse and reappear in the tunnel on the other side! We must have been the first there for 100 years or more.
In the level was a lovely large oak "sink" for want of a better word, collecting water from a fault just above it and an iron pipe fed the water away. A miner had shoved a bit of tin-sheet in it to aid the drip-collection. An interesting feature. Some old tallow candles were still on the walls.
So we followed the level that was nicely decorated on the floor with cave pearls and other calcite formations, for all of 20 feet, until it reached Chamber 14.
And Chamber 14? Totally run-in. Figures! Nothing to be gained in there, no hope at all. Still, nice to see the interesting short bit of level.
Beneath my steely exterior beats the heart of a dashing hero