Sweet Chestnut

You have cracked it. A common British tree. Thanks SD

I am back again with another suggestion; positively the last one. Would you mind looking at Sweet chestnut. Castanea sativa?
http://www.countrysideinfo.co.uk/tree_ga...
To my eyes it looks similar.

Close up of leaf is very distinctive with jagged edges.

I am familiar with mango the leaves are larger. The Mango at Kew has fruited for first time in in 20 years, but it was inside the Palm House.
This tree is outside. I better get a close up of the leaves.

Would it be possible to get a closeup of a leaf? And if you could crush a leaf and smell it....the confirmation (mango) would be instantaneous.
The Royal Botanical Garden at Kew has a fruiting mango tree...so perhaps the odd mango tree might have survived. Good luck with the ID.

Yes I thought the same but they are tropical and would not survive a winter in the UK could it be a chestnut??

Looks like Mango to me.