That 'thing' in the photo above is the protective case of a tiny moth called Coleophora ibipennella. The larva lives inside this peculiar looking construction and feeds (upside down) on an oak leaf before pupating within the case and emerging as a slightly less peculiar looking adult. Despite there being well over 100 species in this genus, feeding within cases on an equally large number of foodplants, I rarely have any luck finding them in their larval stage. Coleophora ibipennella seems to be an exception, with this being the third case of this species that I've found so far in 2016. I stumbled across it whilst taking a jaunt through West End Common in the sun yesterday evening.