I have never seen this before

I have never seen this before

Observation - I have never seen this before - UK and Ireland. Description: Square stem feels quite coarse small Mauve/pink flowers about 1/3 inch long the whole plant stands about 2 feet high and has lots of flowering branches. this has suddenly appeared in my potato patch that was farmland about 5 years ago.

Square stem feels quite coarse small Mauve/pink flowers about 1/3 inch long the whole plant stands about 2 feet high and has lots of flowering branches. this has suddenly appeared in my potato patch that was farmland about 5 years ago.