Apatura Iris. alas is now almost extinct due to habitat destruction
but it was more common before World War I.
The Purple Emperor is a magnificent and elusive insect that is actively sought out by the many subjects of "His Majesty", as the male butterfly is affectionately known. This butterfly spends most of its time in the woodland canopy where it feeds on aphid honeydew...
The male butterfly is one of the most beautiful of all of the butterflies found in the British Isles. From certain angles it appears to have black wings intersected with white bands. However, when the wings are at a certain angle to the sun, the most beautiful purple sheen is displayed, a result of light being refracted from the structures of the wing scales. The female, on the other hand, is a deep brown and does not possess the purple sheen found in the male.
more at the Purple Emperor website.
Purple Emperors have two modes of flight. First, in windy conditions and when chasing, they use a powerful rapid wing beat mode, with wings rising up and down through a 150 degree spectrum. In calm conditions they skim, often at speed, with hardly a wing beat. The females tend to use the latter mode most, though they can certainly put on speed when they want to.