Could it be ash? What were the buds and bark like?

Certainly looks like ash to me, Fraxinus excelsior, a very fancy name for a grotty weed. You could pot it up and care for it, in case it turns out to be something gorgeous, though...

No definitely not ash, I already have that. I am also fairly experienced and this one is a puzzle which is why I posted the pic.

Lovely comment Teadrinker - can we add sycamore to that category?
I thought ash as well - will be interested to hear what it is then.Nothing else other than walnut in my tree book, except the American bitternut which seems a tad unlikely.