A pygmy moth (Lepidoptera: Nepticulidae) on a blackberry leaf (Rubus sp.). Most pygmy moths are leaf miners, that is their larvae eat their way through the insides of leaves. There are several species that have this single white stripe across dark grey wings, with white legs and and an orange head, but I suspect this specimen is probably Stigmella aurella (=Nepticula aurella=Stigmella fruticosella). Firstly, S. aurella is widely quoted (eg: here and in Insects of Britain & Northern Europe by Michael Chinery, Collins, 1993) as being one of the commonest of this type of moth in the UK and, secondly, it specializes in mining Rubus. The matches for the following species are not as good: Stigmella pretiosa (found in Scotland but not in England), Stigmella plagicolella (mines blackthorn and other Prunus trees, but not Rubus), Stigmella salicis (mines broad-leaf willows, but not Rubus), Stigmella obliquella (mines smooth-leaf willows, but not Rubus), Stigmella tityrella (mines beech trees, not Rubus), Stigmella microtheriella (mines hazel and hornbeam, but not Rubus), Stigmella luteella (mines birch trees, not Rubus), Ectoedemia occultella (mines birch, not Rubus), Ectoedemia heringi (mines oak leaves, not Rubus). Of course, it is possible that this moth was only on the bramble leaf by accident, and that its larva had mined a leaf on a nearby tree.
Photo taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2009-07-16.