First butterfly I've seen this year. This is quite early to see a Red Admiral- they migrate from North Africa and the continent during spring and summer. Butterfly Conservation notes "There is an indication that numbers have increased in recent years and that overwintering has occurred in the far south of England".

 I suspect this one has indeed overwintered. The wing edges are rather raggedy which is characteristic of butterflies late in the season. And this one was decidedly sleepy, basking in the sun and not flitting away as I drew closer. Seen in Hitchin, Hertfordshire which is not that far south.