Plant identifcation

Please help me id this plant and also advise th best way o getting rid of it. I have been trying for 15 years (previous owner put it in). No amount of digging or other form of control gets rid of it.
Arghhh! please help
Stew
0
Posts
Is this one plant that's stayed all that time or a plant that seeds about and you keep getting more?
In the sticks near Peterborough
Smooth sow thistle. If you cut it it branches and regrows. You need to fork it out.
thank you for your replies.
nutcutlet: I never let it seed and the roots spread.
fidgetbones: I looked at google images. The leaves on smooth sow thistle seem to be more pointy than the plant in my garden and the flower is purple (not yellow) on the plant in my garden. It looks like there is no diggiing it out because even a tiny bit of root will grow. I would need 100 years to sieve the soil (which is clay based).
Could it be some kind of herb. The previous owner of our house had a herb patch. The garlic and the chives are a bit of a nuisance but are controllable. The plant in question here is a nightmare.
stewpot
Let us have a photo of it when it flowers?
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.