A small, rather uninteresting-looking annual plant of woodland, somewhat like common chickweed (Stellaria media), but with three distinct, almost parallel, veins in each leaf.
All names: Moehringia trinervia (L.) Clairv.; Arenaria trinervia L.
NBN Atlas mapping: Species account : NBN Atlas UK Species Observations database
iNaturalist: Species account : iNaturalist World Species Observations database