How does that work with a hedge?
The house beyond us has put up a leylandii. They planted it as close to their border as they could and it is now 3m high. We kept our fence but no one else did so the hedge has taken over nearly 1m of their garden, for a length of over 50 metres. Apart from our short bit there may be no evidence of where the fences used to be, so could the owners of the hedge claim the land that it has overgrown?
The cannot claim land under the spread of their trees.
Leylandii rules are more dealing with their height and blocking out areas.
Me---F aaaa F2 ---you
Rather than thinking about the fence - think of the land and who can and cannot use it.
So I have fence F and you own land aaaa
Then you stick up a fence or any barrier at F2. Now you cannot get to aaaa.
Then my fence F falls down or I take it down. I then start using land aaaa and you cannot use aaaa. I have a claim for the possession of aaaa.
Over time this claim becomes stronger and in the end I can get the land registry to give me the title to it. Basically a squatter can overturn a legal title.
Hedges are usually measured to the middle but then if it is a hedge and ditch it is to the middle of the ditch.
In your case if you or those on your side of the row of trees maintain that side and use the land while the trees prevent the person on the other side from accessing your side then you can start treating the land as yours. But it only needs him to come round your side once a year to trim a few branches (or perhaps even lean over the top) for him to maintain ownership as he would then still be using his land.