If the squatting law to establish rights is only ten years there. Your new father in law should be cognizant of that fact already or at least made so. Only he can do anything about it legally basically if required.

Unregistered to the occupant other than paying rent or whatever to the real landowner and a good paper trail to me would represent the potential of a claim. It could get complicated and expensive really fast. That's if the ten year limit was exceeded and he could easily lose. Possession as they say at that point is 9/10ths of the law and harder to contest. The squatting has been allowed.

I think a properly registered get off my land notice or court order is indicated. Or some type of legal agreement that totally nullifies any claim being made is needed pretty soon. Verbal statements and agreements would be pretty much worthless. What I was here thinking about is how much area could a squatter claim? Whatever he uses?

It would be highly self negligent to let ones own property become liable for a claim. I suspect that is also the position a court might take after ten years and that is approaching from what you have already learnt.