A couple of years ago, our neighbour's oak tree blew over in some high winds. Although our oak looks the same vintage, its position means it might be less vulnerable.
However it has developed a few dead branches and one of the live ones was growing worryingly close to our roof so we decided to get it trimmed back. One of the tree surgeons we asked to quote thought that it might be safest to have the whole tree cut down but fortunately we found another who felt that a 40% reduction would be enough to save it. The tree man from the District Council, who had a look because there is a Tree Preservation Order on the oak, agreed.