http://i86.photobucket.com/albums/k8...volunteer1.jpg
It's not an ideal photograph, but I'm fairly sure that it's Sycamore (Acer
psuedoplatanus); IIRC the Scots call the Plane. I'd think you'd want to
get that out before it undermines the wall.
Do sycamores undermine walls?
I have a huge tree about 6' from my house. Should I be worried?