Small tortoiseshell

Aglais urticae - Bright orange and black wings with white spot in fore wing which distinguishes it from the larger and much rarer Large
Tortoiseshell.  It is much less numerous now and one reason could be the increase in numbers of sturmia bella - a parasitic fly that lays its minute eggs on the plants where the caterpillar larvae of the tortoiseshell are likely to eat them.  The eggs hatch inside the caterpillars but avoid the vital organs so not killing their hosts for long enough to allow them to pupate