I'd wondered about Ailanthus too, Sharon, but it doesn't fit. The ID tree has toothed leaflets whereas Tree of Heaven's are smooth except for the large projections at the leaflets' base, see:
https://www.google.ca/search?q...
If miss_ee or someone she knows is a member of the RHS they would likely be able to identify it if we can't come up with something:
https://www.rhs.org.uk/members...
