Yes, this is a very poor photo, but the garden warbler is not the easiest of birds to see. They are very drab, in fact they are noted for having no distinguishing features at all. They tend to skulk in foliage for long periods singing, then quickly moving to another perch where they vanish and start singing again. The one way to identify them is their song - a long rambling, flowing, bubbling warble. There are several garden warblers in the woods at the south end of the estate. Hopefully a better photo will follow, but now the leaves are thick and the young have fledged, it probably won't be until 2018...