Next door think my garden is theirs....

Jenniefour

If you decide to fence off then put in gates where the right of way is to allow continued access.

Norman_Castle

The owner or letting agent might be misinterpreting the right of access.

moneyistooshorttomention

I'd have that fence ready to erect literally "the day after" the next door tenant moves "to a better place". If you can't do it yourself/get a workman in that fast - then have something temporary ready to put up there pronto to do the trick whilst waiting for a workman to come in (maybe some of those wooden garden containers one puts plants in and that have trellis fixed along the back of them).

You won't be intruding on someone's "last days here" - but you'll be making the "lay of the land" completely clear before the next tenant has a chance to even see the place and decide to take it.

MrSnuggl3s

Yeah, these things are always slightly difficult to convey without coming across as too passive-aggressive! Maybe knock on their door, ask if they fancy a cup of tea sometime and to chat about the garden.

If they are comfortable with you, they're less likely to kick up any fuss (even if legally they're in the wrong!). A detailed conversation over tea might be too British but it could save you a neighbour-shattering argument when it comes to land ownership!