Does anyone know what this might be?

[Mangotime]

It pops up all over one particular bed…. It’s on a runner/rhizome. I generally snip it when I see it so I don’t know if it ever develops into anything?
We’ve been here 11 years and it’s not particularly causing us any bother but I’m just interested.

The pland id app is suggesting chicken weed or soapwort, but neither of them have runners. Might be wleasier to tell if you let it grow more, but you probably don't want that.

Soapwort, which has long stems that can run along the ground,although I don’t think they take root like true runners. Attractive flower,so might be worth leaving a stem or two.

Brilliant thanks. I will leave it this year and see what comes.

It looks like lysimachia candela which does run off rhizomes. Could have spread from a neighbour's garden?

But that doesn’t have the parallel veins that you can just see in the picture