Can you please identify this plant / weed?

Hi
This popped up in the garden recently and I’m guessing it’s maybe a weed as I didn’t plant anything there!
It started as purple shoots and now has leaves. My plant ID app is not helping at all!
Thanks!

 

I really want to say dahlia as my brain refuses to engage today?!

 

Ah interesting! I won't dig it up then. Sounds much better than the Sun Spurge that my plant identifier app suggested! Thanks.

 

I don't think it's a dahlia ,spurge of some kind comes to mind.
Cut a leaf off, if it has white milky sap, its more than likely a Euphorbia.