perenial candytuft. its a lovely plant and does well in shade too.

Thank you Seaburngirl. Yes the first time I posted the question I forgot about the photo. I wonder how it got into the wall.

it will have self sown. they have seed pods that produce quite light seed. the botanical name is Iberis sempervirens.

Thank you Seaburngirl. I have found it under Iberis in my flower book.