To the best of my knowledge civil liability in this country is covered by the Torts Acts of I believe 1888 or thereabouts and there is an underlying principle of there being no liability without negligence. I person who enters a disused mine while equipped for underground exploration would very likely be viewed by a court as a 'potholer' and everyone knows that potholing is dangerous. A casual passer by who enters an unguarded entrance and suffers an injury could well be regarded quite differently. An open shaft near to a public path would constitute a Statutory Nuisance as well as posing a civil liability risk for the landowner.
There have been 2 recent cases that could well set a precedent for anything going before the courts.
The first concerned an off road cyclist using a Forestry Commission track who came of his bicycle and injured himself. The court rejected his claim for damages.
The second is much more to the point as the judge gave a very explicit reason for his judgement.
A person was using a pool owned by the local authority for diving and as a result injured himself. Rejecting his claim for damages the judge described "those who indulge in adventurous activities should be aware that they do so at their own risk" or similar words.
I participate in the Ceredigion Mines Group who has regular meetings with representatives of interested parties and stakeholders such as the Ceredigion County Council. The County Council take the reasonable view that they have duty of care to prevent persons from accidentally falling into shafts or entering workings, but not to prevent anyone doing so deliberately.
I rather fear that it will take more test cases to define the position clearly, however in view of previous bruising in the courts its unlikely that any ‘no win, no fee’ outfit will want to touch it, which basically is a double edged weapon from our point of view.
My avatar is a poor likeness.