Coz weem in kerrnaww, basically if you dig a hole in the ground it's like hopping a fence into someone else's paddock. Similarly, if you find yourself presented with an already gaping hole in a "here's one I made earlier" fashion, it's essentially a garden gate into someone's manor.
You hear "mineral rights" thrown around quite a lot, but it's really an archaic metaphor for underground real estate. If you go down a mine it is unlawful trespass against the "mineral rights" owner.
Now, expecting the surface landowner to pay for shaft capping is really like asking the highways agency to pay for your front door if you live on a street.
There is a bit of weasel room though as to where the boundary between surface and underground land lays, and this is reflected in your full title deeds or last explicit conveyance. Look for "within", "upon" or "beneath/below" as these detail whether or not surface aggregates (sand, clay, spoil dumps, etc) are reserved from the title. Most land in the county formed part of a manorial and so if you find subtractive conveyance that relates to the relevant manorial it will detail reservations.
I think there is a statute 3ft of shite below surface which the freeholder can play with, however this has only been proved by legal precedent and not hard law. It'll allow you to lay shallow foundations but not bury your victims standing up...
Enough rambling though, the fact of the matter is that in numerous cases it has been proved that the min rights owner has had to pay for remediation work. Occupiers liability act - yes, "occupiers"; this means lease holders as well - requires surface matey to put up adequate fencing.
Refer to your solicitor. Internet forums are full of weirdie beardies (like me) when it's "awfully important & sons" signature that you need.