Thanks everybody - you're expert knwoledge is gradually making me more familiar with the natural world and trees surrounding me. If anybody could help identify these below, that would be handy ...
I don't recognize it from the foliage and overall habit.
(The twigs look too slender for the tree, somehow)
Are there any old fruit (beries, seeds, nuts, pods, etc.) amongst the grass under the tree, remnants from last year? If so, it would help a great deal if you could photo/describe them.
Where is it?
OK - London - so it must be quite hardy to have got to that size.
There are many trees that I have ruled out because the leaflets are toothed (Sorbus, Fraxinus, Carya, Pterocarya...)
Those leaves remind me so much of Cestrum nocturnum!
But it can't be, because that never forms such a substantial and single-stemmed tree (it is also not hardy enough to survive long enough to do so).
See if walnut fits.
One useful thing to look at is the scars where leaves have fallen off.
This is what that looks like with walnuts
You'll see from your photo that some of the leaflets are staggered along their stems (not exactly opposite). That does happen with walnuts, as shown in the picture here.
The tree is old enough to be fruiting, but the UK spring and summer may not have been conducive to fruit production this year. But you could still find walnut shells (whole or part) under the tree.
However, the leaves are not right in other ways for either of the common walnuts (Juglans regia, nigra).
So this is still merely thinking out loud.
I took a look this morning - there was no fruit underneath and no expsed bits like the above.
The branches were covered in moss though, in a way the surrounding trees weren't.
Shall I take another picture of any part of the tree to help?
Thanks for the further photos.
They should help, but they don't, at least not to me.
I thought I had it (Fraxinus ornus), but there are several aspects of the leaves that are not right (and it is not F. angustifolia, either).
It also looks a bit like Trichilia glabra, but that is not hardy (from sub-Saharan Africa)
(T. hirta is also similar.)
All I can suggest is:
- waiting and watching for flowers and fruit
- referring to local knowledge: perhaps asking at Capel Manor Horticultural College (nearby)
If you make any progress, please post here again!
If anybody else has suggestions, please post!