Bit hard to see, but it could be Cardamine pratensis.

I think it looks like Greater Stitchwort, of which we seem to see less and less. A lovely, dainty little flower. There is also a Lesser Stitchwort.

Thank you both for helping me.
Google tells me that there is a pink version of stitchwort that grows in Devon but then suggested Pink Purslane which does look very much like it.

Claytonia is not native to Britain though.