This tree has a fungus called Ganoderma. It can live inside a tree without killing it if the tree is vigorous enough in its annual growth increment. Basically the tree needs to out grow the fungus and throw some chemical barriers up against it to slow or stop it’s spread.
Due to the large fungal bracket on the stem, we opted for a heavy crown reduction/pollard. This serves to re-invigorate an Ash tree and apply less stress on the roots and vascular system.
Also the sail effect or strain on the structure is significantly reduced.