Somebody has tried to dig Keldhead in the past but were seemingly stopped by the National Park. The problem is that there are a few collapses very close to the entrance and the only place to dump spoil is outside of the mine which the Park objected to.
Slightly unusually for the northern dales, the level is in the bottom of a main dale, almost roadside and near houses.
If you can be bothered to hunt it down there was an article about it in (I think) the Observer Gardening Supplement, that bible of all Northern undergroundness...