Gribela writes
I'm fairly certain it's a Fraxinus - it's bl**dy enormous! I think the
wall and the tree have had plenty time to get acquainted - they both
pre-date me.

Fraxinus has black terminal buds, especially obvious in winter. Very
easy way to identify it.

And if it's that big, you'd recognise rowan by the big bunches of white
flowers followed by orange berries. Ash seeds are 'keys' - green winged
things.
--
Kay