When I started writing this post I thought I'd found a Silver studded blue butterfly which would have been quite something as it's not known to inhabit Herefordshire where I photographed it. However after extensive research I've come to the conclusion that it's a Common blue and, though pretty, not of earth-shattering significance. Perhaps the most identifying feature that I could pick out is the way the patch of grey on the leading edge of the hind wing has a thin branch spiking out from the main grey area. Also, the band of grey that borders all the wings (just inside the white outer border) is very narrow and would probably be thicker in the Silver studded blue. The usual rule of thumb for nature spotting also applies: assume it's the most common thing unless you've reason to think different! And if you think you've made a groundbreaking discovery, you've almost definitely misidentified the species!