This cute little violet, which I thought was the Labrador violet (Viola labradorica), seems to be more likely to be Viola riviniana 'Purpurea' (ht 5 cm), a very similar plant, known colloquially as the purple-leaf dog violet or wood violet. The tiny flowers are a vibrant shade of magenta-purple and the leaves are purplish-green, making a good combination. It does spread by suckers and it self-seeds very enthusiastically, but it makes such a pretty carpet where there is room for it, in a wilder part of the garden. It is found in Europe, Iceland, North America and Madeira. It is quite cold hardy. It will grow in sun, part-shade and even full shade, including where it is quite dry, apparently, but it does best if there is some moisture in the soil.