What a fab post, thank you. That made me laugh. And you're right, it's a seriously deep hole, I hadn't thought about it either. The top of the "shaft" is quite wide, if the hollow that the capped water supply sits in is it (see my pic). It has signs up saying "Danger" and is fenced off (no, I didn't investigate further).

I love your description of the person on the rope dangling down into this hole. Perhaps it was a treacle well? Actually there's a pub in Hereford called the Treacle Mine. Hmm.

The name thing is very interesting. Gatley Park is really close to where I grew up, and is even closer to Croft Ambrey, another of Herefordshire's excellent hillforts. Wapley doesn't seem to have a chunk out of it, apart from the shaft, although there is some quarrying at the western end of the fort.