A bit more information:
Piper’s Hole 1 aka Pipers Hole No 1, Tresco, Isles of Scilly
NGR SV 166 887 A 0 m L 90 m
Pipers Hole is a rather interesting cave situated on the rugged North coast of Tresco, Isles of Scilly. The cave itself was at one time very difficult to find, but has now become a popular tourist attraction, and sign posts leading to it are found all over that part of the island. Such an attraction has it become that in the outer parts wooden planks cover over the loose boulders and steps lead down to the edge of a small fresh water lake in the interior. Inevitably, of course, it has the usual charming folk lore surrounding its history. Legend has it that during the attack on the islands by Cromwell's men under Admiral Blake in 1651, a young officer was captured by the Cavaliers. He escaped and hid in Pipers Hole, where he was discovered and looked after by the daughter of Sir John Grenville, Commander of the Cavalier forces. She fell in love with him and soon effected his escape. After the capitulation he returned and married her.
Just how much of the cave was formed by the action of sea water and how much was due to its possible development as a tin adit is difficult to estimate. However, since the sea only enters the cave now in storms, and the surface of the land is pitted with entrances to further adits, it is likely that the majority is due to tin mining.
A pile of boulders in the entrance makes it low enough for one to have to stoop to gain access to the interior. The boulders extend for about 30 m in to the cave, but shortly after the entrance the roof becomes high enough to permit standing. There the boulders reach the edge of the lake, the walls rise vertically upwards for over 6 m to give rise to a chambers about 10 m long and about 2 m wide. The lake occupies about 9 m of the floor space of the chamber, and its waters are about a metre deep. The bottom is covered with mud and a few boulders. The lake may easily be traversed by a small rowing boat supplied for the purpose. At the far end of the lake is a sand and shingle beach which extends back for 3 m until it meets the continuing passage. This passage continues fairly horizontally into the granite, and its furthermost point, the end of the cave, must be about 45 m from the shingle beach. This passage, too, is covered with a very coarse sand at its bottom, and the roof varies considerably in height.
Perhaps-the most interesting thing about the cave is the gradual of decomposition of the granite by the percolating rain water. The felspar in the granite has been decomposed by the carbonic acid content of the rain water and this is probably enhanced by the thick layers of peat overlying the cave leaving the walls of the cave coated with Kaolin in its plastic state. This is especially noticeable in the inner recesses of the cave. The sand and shingle floor may well owe its origin to the mica and quartz crystals not decomposed by the dilute acid.
Thus, whether or not it is a mine in origin, it is certainly being enlarged by water action, and therefore perhaps deserves the title of ‘cave’.