Sorry the flash came on for the first pic, but at least it shows the root/stem formation a bit. It isn't the same as the fat hen weed you all identified for me, but I have been watching it (them) in the hope they were going to be something nice and I suspect that they are not!
Do the roots smell of cloves? If so, it's wood avens.
or scrape it and see it you get orange juice for greater celandine
Greater celandine it is then. Well done NC. (Waterbutts I dug up a few acres of wood avens backalong, so I recognise that now!) The roots look bizarrely like developing carrots and as if they'll be horrible to remove once they take hold. I shall pull it all up from the beds today. Presumably it is a pernicious and unhelpful weed which is impossible to eradicate and grows from the weeniest bit of tap root?
No, greater celandine just seeds about, not a lot of trouble to get rid of but seeds must last for years in the soil and forever appearing
Thank Goodness for that, I've just pulled out 2 trug loads but it comes up really easily (unlike all the other nasties I found en route)! Anyone know how to get rid of holly seedlings without digging the whole bed up?