In message , Janet Tweedy
writes
Liquidambar is another possibility

It's probably Euonymus alatus, and I got confused by the absence of the
typical autumn colour. The location is an abandoned arboretum planted
with native species (was it planted by mistake, instead of Euonymus
europaeus).

It's not Ulmus alata, which has simple, alternate leaves, and not
Liquidambar styraciflua, which has palmately lobed leaves. (I was
wondering if I was forgetting anything obvious.)

But thanks for the suggestions.
--
Stewart Robert Hinsley