A close up of the leaves and the bark would be very usefull for an ID.

Thank you Loosestrife2 I've added a picture of the leaves.

Thank you for the photo. Being from the USA and using that point of view I will say that the leaves look very much like the leaves one sees on a wild cherry tree, Prunis aveum. Did it flower early spring with white flowers? If so then that is it.

This is the problem, it's in a friends garden. The house has just been bought and they're not sure wether or not they wish to keep it, depending on what it is ? So, they've never seen any flowers as only been there a few weeks.

Then my advice is to have them delay their decision until next spring to see if it is a ornamental tree which just needed a little pruning and TLC. Irregardless, given time, they may grow fond of it and decide to keep it whatever it is:)