Is this in the UK?
If not, where?
Can you give any description of the flowers and fruit?
(there might be old fruit from last year on the ground somewhere, assuming the mower hasn't disposed of it)
Thank you for your help so far, the tree is in my garden in Broxbourne, Hertfordshire, I've attached a pic of the flower/fruit I found at the base of the tree.
Unfortunately, other than making me think Magnoliaceae, which didn't get me very far, I' confess I'm stumped!
If you can photo the flowers in due course, that could help a lot.
I've been searching images online for clues, I've seen a fair number of pictures that seem to look very similar, they are mostly of Pecan trees, could this be a possibility?
No - The leaves are very different - they are pinnate
I wonder what pictures you've been finding...
However, I've had another thought...
You tree might just be a loquat, Eriobotrya japonica...
[photo from http://www.itmonline.org/jintu/oldmen.htm, with my thanks]
It is rarely grown in the UK, not least because the climate is usually non-conducive to fruit ripening.
Do a bit of research and see if it fits.
Just a thought...
Perhaps the previous owners went on holiday, and brought back some seeds (they are rather nice seeds - like varnished mini-chestnuts). They are common small trees here in Cyprus (where I live), reasonably attractive for greenery and mid-scale structure, and they can also serve as providers of shade. The flowers are nice though not spectacular, as are the fruit.
If you think of it, keep us posted on yours - it would be nice to know when and how well it flowers, ditto fruiting.