The Red Dead-Nettle or Purple Dead-Nettle (Lamium purpureum) is the little sister of the Spotted Dead-Nettle. It is an annual or biennial and its growing season is either autumn to early summer or spring to summer.
In mild years it can flower as early as November.
Also pictured above are the white flowers of Chickweed (Stellaria media) and the leaves of Burr Chervil (Anthriscus caucalis).
The picture below shows that the flowers are not always light pink or dark pink. There is also a white flowering form of Lamium purpureum. This seems to be relatively rare. Apart from the fact that it used to be called Lamium purpureum var. albiflorum, I could not find any further information about it.
Red Dead-Nettle is a member of the Labiatae family. It is closely related to some popular culinary herbs such as Basil, Thyme, Oregano, Marjoram and Sage.