According to https://forums.groundspeak.com/GC/in...post&p=4931369, the National Park Authority refuse cache permission in their owned woodlands. I'm not sure of the extent of these, but it could be worth checking with the contact and confirming;
a. that he has a proper understanding of what a geocache entails and hasn't made incorrect assumptions; and
b. that the restriction is confined to woodland only, and which woodlands this is relevant to.

Once that has been established, it sounds like a very useful addition to the Landowner Agreement page (although likely to be a negative one).