Allow the tree to decay naturally.
Why is this important?
This tree is 270 years old and it was always there. It won't fall suddenly itself. Despite the risk assesed with its condition the alternative for allowing the tree to decay naturally could be reavulated and taken into consideration.(e.g. providing supporting construction to the tree).
Trees are essential to our existence. They provide us with oxygen, reduce carbon and give life to the world's wildlife. Saving our trees will reduce greenhouse gases, protect our wildlife and bees, and make sure our environment and communities can be enjoyed by future generations.