I'm pretty sure this is Boucing Bet (aka Soapwort, Saponaria officinalis). But that's supposed to have 5 petals, & this one has 6! I have a shot of the leaves I can upload, if that will help.
Common Soapwort (Saponaria officinalis) is a vespertine flower, and a common perennial plant from the carnation family (Caryophyllaceae). Other common names are Bouncing Bet and Sweet William; locally it is simply "the Soapwort" although there are about 20 species of soapworts altogether.
