The tree is their property - your garden is your garden. Talk to your neighbour and say you need to cut it. As far as that encroaching on your property they cannot argue. Technically the cuttings belong to them, so do not dispose but give them back
thanks, but the tree is a young tree, dont ask what type i have no idea, i would need to cut off about 4foot the top of it, and the house is empty hes in jail, so noway to ask,
thanks again.
Just check its not a protected tree if you're going to cut it yourself - even though you are entitled to cut anything overhanging your garden, you will need the Council's permission to cut it if it comes under a Tree Protection Order.
Slight correction to Law Student's answer. Leaning over the fence, cutting off the branches and keeping them does not technically amount to burglary. Burglary is defined as "a person who enters a building or part of a building as a trespasser....". The garden certainly isn't a building nor does it form part of a building. You would be committing theft though as Law Student rightly points out, if you fail to give the cuttings back to your neighbour.