Wonderful weed: the Red Dead-nettle (Lamium purpureum). It appears all over the place at this time of year and keeps on flowering well into autumn. Lamium species are much frequented by bees so the long season of this one makes it an important source of nectar and pollen. It's a diminutive but prolific annual that thrives on disturbed ground be it in the town, city or countryside; the patch above is on the allotment.