Keble Martin, in the 1969 edition of The Concise British Flora in Colour, describes this plant as “Naturalized in woods, etc., in W. Cornwall, S. Wales, S.W. Ireland and Guernsey”, and the flowering period as April to June. Since he spent much of his life in Devon it seems likely that it wasn’t found here at the time he was writing. It’s now an invasive garden weed and common along roadsides and on disturbed ground as well as in woodland. The Collins Complete Guide to British Wildflowers (2006) describes it as “Introduced and naturalized locally in the south-west”. They give a flowering period of March to June but this picture was taken on December 31st and I had previously seen another plant in flower on December 17th.
Status: introduced and naturalised locally in the south-west.