This is an ancient Ash tree which grows on the boundary of our land. It has been dieing all the time we have been here, although in the first few years it did manage to grow a few new branches and twigs. However, the last ten years it has been standing there rotting, and various big rotten branches have fallen/been snagged on the other upright trunks (it split into 4 different upright trunks - perhaps having been pollarded when a young tree - which was probably 200 years ago or so).
Anyway, Tam was checking the oil tank for us yesterday when she heard a tremendous crack and crash and another upright of the tree fell down, bring two big snagged boughs with it. We went up to check it out.