Little stars

I'm flummoxed. Despite much research I am unable to determine what these little flowers are. I'm pretty sure they are not wood amenone as there are no serrated leaves. Also they are not in a wood but on an embankment by the canal, and the ones in the wood are past now. So if any of you have theories or blinding certaintities, I'd love to know. (They are a similar size to wood anemonies.)