Dont worry about it, I can shoot holes in it right of the top of my head. What lies under land (from the arguments in that particular paper) are as irrelevant as what lies above. Land ownership was once regarded as all the way to heaven and all the way to the centre of the earth. Obviously this has been overturned in recent years due to aviation acts which allow ownership to extend all the way up sufficient for quiet enjoyment only, otherwise overflying aircraft would be trespassing. Likewise we now know that the centre of the earth is a liquid state.
The very idea of every metre of cave space being shown on 'Definitive Maps' if CROW were intended to extend to them is ridiculous anyway.
I have an 'opinion' which I keep to myself, and yes it is based on current legislation, and angle everyone else has missed. But, the expression "collateral damage" comes to mind, also "can of worms". No, it stays in my head, for good.
Please, no PMs on this, the answer is "no".