"Red campion". Licensed under CC BY-SA 3.0 via Commons
Bizarrely I didn't take a picture of Red Campion, Silene dioica, so this is from the amazing resource that is Wikipedia. Red Campion is a bit more widespread than White Campion, growing up to 1000m altitude whereas White Campion is confined to lowland areas, especially those with calcareous soils. It grows at the back of the pond in the garden.