The adit is some distance from the building. It has been blocked by soil and stone from some of the "hardscape" works. I'm sure it can be easily reversed. However, questions of access and liability need be addressed; it's right next to a well used public footpath. Penrhyn/Rigcycle may have an opinion! It's their only drain! I'm very suprised that this wasn't in "the property paperwork" and that they've not, as yet, made any comment.
It used to be a popular entrance; the University Caving Club were regular users, so I'm told.