Our neighbour who we share the back boundary with, has a lovely old oak tree in their garden. It must be at least 40ft high. We have never met or had a conversation with them. Our house was was built 13 years ago and was previously fields. We have lived here 7 years. A significant proportion of the tree overhangs our garden and our separate garage. The lowest branches are about 8ft high over our garden and rest on the garage roof. We would like the tree cut back significantly, as it blocks so much light. Who is responsible for this? If it is us, do we have ask their permission? I know that it will need a tree surgeon. Any advice gratefully received.