I think this is Salad Burnet

It looks like it. Sanguisorba minor. It grows in the hedgerows around here.
I don't know if it's invasive. I've got a few Sanguisorbas and they're well behaved, but this is a wild form so I don't know.

Oh Hywel that was the other name I was thinking of..
If it grows in hedgerows around you could it have come with your seeds you kindly offered me last year?

it also reminds me of silverweed. but i think it is also salad burnet. the leaves smell and taste like cucumber if that helps with id.

It isn't with the seeds I sent you Meadowland, I collected those from a pod on the plant, which is in a pot in my garden. I put the pod in a container and shook the seeds out and those are what I sent you.
There's no Salad Burnet growing in the hedgerow at the bottom of my garden anyway, they're in more open areas :)

There's Silverweed in my garden but it stays in the same place. I pull the runners out but I wouldn't say it was invasive at all, although if I left the runners alone it would spread a bit.

Thank you Hywel for updating me.It must be a rogue seed from here.
Thank you Eileen!