I don't mean to sound negative and I fully appreciate how you feel but if you do kill a mature tree in-situ, then it's going to fall down anyway at some point. This will probably be when and where you don't expect it to, thus causing substantial havoc and damage. Since you will then need to dispose of said dead, fallen tree you would be better off paying for it to be professionally felled (or at least pruned) in the first place. You might also like to consider that some species are protected and also that whoever owns the tree may not be amused by it's sudden demise.