"Bob Hobden" wrote
The nearest we got was a large "Great Banded Grayling" but that isn't
jet black and the white patches link up which they didn't in the one
we saw. It was the flight that caught my eye first, fast and straight,
land and hang about a bit sunning itself on the compost heap, then
take off and gone, no butterfly type wandering about at all.

Are you still ruling out Purple Emperor? It's said have a distinctive
fast, straight flight and your description does sound very like one with
the purple sheen not catching the light. Good photos he
http://www.ukwildlifeimages.org.uk/P...20Emperor.html

I'd forgo any big exotic butterflies in exchange for all our erstwhile
common local ones turning up again. They all seem very rare around here
this summer. My patches of Sedum spectabile used to be covered with
small tortoiseshells on sunny September days past, but today I only
spotted one solitary Red Admiral sitting on it.

--
Sue