Mystery Flower

I bought this plant in a cut-price sale. There was no name on the label and the shop assistants could not identify it. Can anyone tell me what it is please? The bud cases split and turn back when the flower opens, and dying flowers turn pink. The flowers are on long spindly stems. The leaves are in extra shot.

Edit: Riwaka7 has identified it as Gaura.

 Thanks to BikerBear for hosting Flower Friday