Small Tortoiseshell,
Aglais urticae.
Unfortunately, this most-familiar of butterflies has suffered a worrying decline, especially in the south, over the last few years. One theory is the increasing presence of a particular parasitic fly, Sturmia bella, due to global warming. It is believed that the lifecycle of the Small Tortoiseshell is better-synchronised with that of the fly and it is therefore more prone to parasitism.