By Anchorman
Cambridgeshire,
United Kingdom 
Does anyone recognise this plant please? It grows on 45cm stems.I'm told it is perennial. It's growing in a wild woodland setting but may be an escaped garden plant. the flowers are 2.5cm across. It flowers in August. the wider leaves in the background of the photo are its leaves.
23 Aug, 2014
Answers
Thanks for that. It has been suggested on another forum that it is a double form of saponaria officinalis
23 Aug, 2014
I was thinking saponaria. If so, dig it out (and then dig it out again, and again).
23 Aug, 2014
It's Saponaria :))
23 Aug, 2014
I've a nice spot for it in the wild part of my own garden where it can run rampant without worrying me!
23 Aug, 2014
?Silene officinalis is a possibility. If so do not bring it into your garden, it is a thug of the never removable kind.
23 Aug, 2014