The cave as far as the third chamber and side galleries has been known since at least the Iron Age period. Prior to the construction of a dam at the resurgence to feed water to the paper mill downstream, two more chambers (the Fourth and Fifth) were accessible. Further upstream the way lies underwater. Diving was first tried by the Cave Diving Group under the leadership of Graham Balcombe in 1935. With equipment on loan from Siebe Gorman, he and Penelope ("Mossy") Powell penetrated into the cave, reaching the seventh chamber, using standard diving dress. The events marked the first successful cave dives in Britain.