This is Dianthus 'Messines Pink', one of the Mule Pinks, dating from before 1933. There is a story told of this 'pink' which is that a soldier, wounded in the Messines Ridge area, was found holding a piece of a plant in his hand. When he was returned to England he was still holding it and it was planted and this gave rise to Messines Pink. Whether it's a true story or not, I love the myth and legend that gets attached to plants!