Question
I live in the UK, in a house with a very mature (victorian) garden.

Recently some new houses have been built behind me, one of the owners of these new houses has approached me to ask me to "do something" witha tree which is rooted in my property but overhangs his.

The tree is a 50+ year old ash? tree, (black buds) and I think it is diseased as it only produces a small amount of foilage in the summer. He is worried that the tree is dead and that in a storm it will fall on his house.

Is there a legal owness on me to remove the tree?

I realise that in law he is entitled to prune anything overhanging his property, does this include very mature boughs of trees?

Answer
David,

First, you're lucky that the neighbor talked to you.  In my neighborhood I would have heard the chainsaw first and the talk later.

Here, if the tree is diseased, and a reasonable owner can be assumed to have known it, the owner is responsible for any damage caused by the tree, even if that damage happens in a storm.  

A healthy tree pushed over in a storm however, is the problem of the property owner where the tree falls, no matter where it was rooted.

And here, someone can cut anything overhanging their property line, regardless of the consequences to the tree.

So... either
(1) get a professional opinion in writing (certified arborist or tree surgeon?) that the tree is healthy, to put your neighbor's mind at ease, and to put him on notice that you're not negligent regarding the status of your tree,  OR,
(2)get a professional opinion that the tree is unhealthy and then treat it if possible, or remove it only if necessary,
OR ,
(3) skip the professional, save some money with a low end tree service to remove the tree,  then plant something there that is more fitting for the newly confined space.

I'd go the 1-2 route.  A fifty year old tree, if brought back to health, could be valuable to the whole neighborhood.

For what it's worth,
Mark in Portland