By Slimdil
Northumberland,
United Kingdom 
Posted similar pictures last year at the same time. No idea what kind of tree this is as it was "planted" by passing birds. No sooner have the leaves opened than they begin to discolour and fall. Last year it was suggested it could be spider-mite bit I don't see any evidence of these on the leaves. Hope it's something terminal as I'd love to remove it from the middle of the lawn, but husband can't bear removing trees!
15 Jul, 2016
Answers
I'm sorry, Slimdil, but I can't find the question from last year, if that's where you posted those photos.
15 Jul, 2016
Just checked and it was actually June 2014 that I asked the same question! I've saved the photos but don't know how to add them to this post. There is a photo of the whole tree there.
16 Jul, 2016
Still not expert enough, but, with the other pictures, it now looks to me like one of the entire-leaved Hawthorns, such as Crataegus prunifolius. The problem looks somewhat like fireblight, but I'm not entirely comfortable with that diagnosis. More likely some kind of fungal leaf spot, but there are so many! :/
16 Jul, 2016
It looks like some kind of pear, to me, but I'm not enough of an expert on cool country trees. A photo of the twigs with attached leaves might be helpful. An overview of the general shape and branch structure might help, too.
15 Jul, 2016