Argynnis aglaja ssp aglaja Dark Green Fritillary
This butterfly was flitting around us as we searched for the Epipactis sancta (Lindisfarne Helleborine). The flower was a disappointment but the Fritillary wasn't. This is the commonest (southern) sub species of Argynnis aglaja the adult of which prefers flower rich grassland such is presented by stable coastal dunes.
The larval food plant is usually Viola riviniana (Common Dog-violet). The books also say that the very early flowering Viola hirta (Hairy Violet) is sometimes used.