Campion family?

Campion family?

Observation - Campion family?. Description: Any suggestions as to what this modest but pretty flower is? Herbaceous, cultivated, leaves in opposite pairs, sessile, on thin wiry purple-tinged stems to about 2' high. Flowers held singly, both terminal and from leaf axils: inflated hairy calyx,

Any suggestions as to what this modest but pretty flower is?

Herbaceous, cultivated, leaves in opposite pairs, sessile, on thin wiry purple-tinged stems to about 2' high.

Flowers held singly, both terminal and from leaf axils: inflated hairy calyx, with a fringe of white petals projecting.

Looks hauntingly familiar but I can't put a name to it (cries of "it's me age!").

Suggesions, please?