@simon_brooke @thecommongreen In England the problem is sometimes that nobody *wants* to admit ownership of a piece of land, because they then might be liable for various costs.
We ( #Cambridge City Council) wanted to resurface a footpath but we couldn't find out who owned it to ask them for permission.
After some research it appeared plausible that it *might* be owned by the Diocese of Ely, but they refused to admit that they owned it, because then *they* might be responsible for paying for the maintenance of the footpath.
They were however, in due course, persuaded to write a letter saying "we do not admit that we own this land, but if we did own it we would have no objection to the council resurfacing the footpath". As there were no other candidate owners identified this seemed good enough (ie it passed our own lawyers' risk assessment) and we went ahead.
Researching ownership of odd bits of land is the sort of task that might be given to a law student doing a summer vacation job.