I think it is probably Black nightshade (Solanum nigrum) but the purple stems and leaf veins are unusual, so not 100% certain.
I think some plants are flowering out of season, early etc @LinusR especially if it's a warmer, more protected area.
I live in west central Scotland - not where that photo is...
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw