First thought was lysimachia 'firecracker' and it will have buttercup yellow flowers in the axils of the leaves. Unless I am wrong which is more than likely.

That is what it is. We have been removing this from our garden for the last 12 months. We spent 20 years removing it from our last garden and it was still there when we moved.

It's haloragis erecta 'Wellington Bronze'

Looking at the image on the main computer I can see that the leaves are very toughed and whilst I don't know
Haloragis erecta 'Wellington Bronze' I agree with Andrew's id Common name is raspwort.
Is it a well behaved plant?

It's definitely not Lysimachia bronze as I have the yellow one rampant everywhere, strangely I had the bronze and it died Owd!
I think you have the answer Andrew as looking it up on Google I remember the insipid tiny flowers which really just need to be removed, they are obviously how I gained a few. I just take them out where I don't want them, but otherwise it's a nice plant and a good foil for some others. I have another one against a vivid yellow little shrub (can't remember what that is either) and it looks stunning.
Thank you all for helping me out.

Need to go to Specsave for better glasses these days. Sorry.