It's not a topiary, this form of growing is known as a 'standard', meaning a long, bare stem or trunk with growth trained at the top. Not entirely sure what it is other than it resembles Philadelphus coronarius, but I can't imagine that any professional grower would create a standard form out of that particular shrub. Has it done anything, like flower, at all? Is the top part growing rapidly? How long have you had it?

The leaves remind me of Catalpa bignonioides, the Indian Bean Tree. They do often make them into standards.

Surely not, Jimmytheone, every Catalpa I've seen has much broader, more rounded leaves? Though a standard form of that would certainly make more sense...

This is in the garden of a new property my friend is buying so not sure how old this is.. it has been grafted on I would say and my local dobbies garden centre say it was topiary which I thought may be wrong...thanks for the comments so far

Could it possibly be Cornus mas?

It does appear to have a graft at the top of the stem - it looks deciduous, so if your friend moves in he might have to wait till next year for it to do something (like flower) before you get an accurate ID.

Possibly a Japanese Flowering Cherry?

Might be - the bark's the right colour... blossom next spring if it is.

I was thinking of Hibiscus syriacus, myself. Both Philadelphus and Cornus would have opposite leaves rather than alternate, as this one has. The leaves are also a little too broad and cordate for a flowering cherry, at least from what I remember from the last time I was in Washington, DC.

Thanks for all replies