Sick cherries on tree

Dear all
Our dwarf self fertilising cherry tree has a reasonable amount of fruit (see photos) but has developed some cherries which are brown and shrivelled - we water it about once a week, and it has lovely foliage, and otherwise looks healthy. The soil is underlying clay (north London) but we made some improvements before planting.

Any suggestions?

William

Hello and welcome to this great site! I have just tried to look your problem up and found this on another forum: http://thegreenlivingforum.net/forum/viewtopic.php?f=12&t=7356. Hope it helps.