This plant is, probably, a rare British native wild-flower, its main population being concentrated in Cricklade Meadow in Wiltshire. These pictures, however, were taken last month at Clyne Gardens here in Swansea, where a small population is naturalised on a grassy bank, along with other wild-flowers.
Most plants are of this dark purple chequered variety:
although a small proportion are white:
Makes a change from Foxes!