White Plume Moth.
(Pterophorus pentadactyla)

This, alas, shows that there is a lot of Bindweed in my garden.

Information:
Unlike most of the 'Plume' moths the White Plume does not furl its wings but leaves the 'plumes' (these are a deeply divided fringe at the trailing edge of each fore-wing and hindwing) visible at rest - quite distinctive. If that is not enough to identify them they are completelly white and have long spiky projections on their legs - also white ... and they are one of the largest of the 'Plume' moths.
Fore-wing length: 12-16mm. They fly (from dusk onwards) June-July in much of Great Britain over dry areas ofgrass and waste ground and may prefer bindweed as a larval foodplant.