On Tue, 6 Aug 2013 09:26:28 +1000, "David Hare-Scott"
wrote:

Lisa T wrote:
My neighbour has a huge oak tree literally on my boundary fence.

Then it is on the neighbor's property line as well... here in the US a
tree on the property line is a no brainer, the portion on your side
gets removed, in fact in most US municipalities if one land owner
wants it gone the entire tree goes... most zoning laws specify a set
back for large trees, may be that no large trees can be planted closer
than 15' from the property line.

This tree is about 30 feet high...

That's not a very large oak tree, but it's not a small tree either.

This is a legal question whose answer will depend on the jurisdiction that
you are in. It is not sensible to ask an international garden group such a
thing as we are probably not in your area and probably not lawyers either.

I concur, get legal advice... and take pictures.