A castle where people live rent-free
bbc.com
bbc.com
It sounded to me like they could live there if they were family of the original inhabitants but not sell that right to outsiders?
Like it's held in some kind of trust for them.
Though it's not spelled out exactly in the article either way.
Castle estates are probably a few generations deeper than US land trusts which would make the problem much worse to deal with.
The world seems to be trending towards renting though.