The leaves seem a little too broad for Calylophus serrulatus, it has really narrow leaves in comparison - yours is probably one of the Oenothera, and these can pop up on their own. I'd keep it anyway!

Thank you for that Bamboo, I can now look it up.

I've never been sure whether these count as wild flowers or garden ones, but who cares anyway since a weed is only a plant growing in the wrong place.

Thank you for that Steragram2 how right you are, I will leave the plant where it is and maybe get some young plants next year to move about the garden.

They tend to seed around a bit Path, so they may do that little job for you! (But they have not much idea of where a suitable place might be...)