Hello there, I am the new kid on the block. I have just joined the forum because I am so impressed with the knowledge of the Matlock area displayed by minerat, sougher, and others.
Incidentally, about the earlier postings on the sump at Devonshire Cavern, on checking my notes, it was dived by Andy Morrison with other members of the Masson Caving Group in 1999. It was then found to be only a blind water-filled chamber, some 20 feet long and 10 feet high. (Webb, Dave, 1999. Devonshire Caverns: the Lower Sump Dive. Caves & Caving, Winter 1999-2000. p6). This point is only a short distance from Gilderoy Old Sough but, when the blockage in that burst open in 1961, the release of its water did not affect the sump in Devonshire Cavern (Woodward, Maurice, 1961. The Matlock Thermal Springs: Further Investigations II. P.D.M.H.S. Bull. Vol. 1 No. 5).
However, I agree that there must be other workings additional to those shown on John Barnatt’s detailed survey, either backfilled or at a higher level near Gilderoy Shaft or further west.
Also I notice that sougher and iclok were asking about the workings under Hodgkinson’s Hotel – see Webb, Dave, 2002. Hodgkinsons Hotel Level Matlock Bath – A ‘Cave’ in a Pub. Derbyshire Caver No 115. pp2-3). This is just an insignificant 18th century vein working – actually on Gilderoy Vein but it does not get anywhere near Gilderoy Shaft on Devonshire Cavern. The Hotel was built in about 1772. It was known as Hotel Mine in the 19th century. There may be blocked levels lower down.
Hope that this is of some interest.