The plant self seeded. Any compost (Homebase) was used around other plants without any ill effect and it is certainly not weedkiller.
I have not heard of fasciation, it may be affected by this, but I still do not know what the plant may be...Any more ideas?
In the background of your middle picture there are leaves that could be evening primrose. re they the same plant?
It's hard to ID anything that's so distorted it's become unrecognisable
It has rained a lot today and the flower head has appeared. It appears to be some type of distorted evening primrose...Perhaps all of the plants I removed and thought were weeds were in fact attacked by the aphids some of the more eagle eyed amongst you suggested.
Thanks for the help.
The plant looks like a Euphorbia of some sort, and the weird appearance is a type of fasciation (look on RHS website). I've got two Forsythias in customers' gardens where this happens every year to a couple of twigs. The stems become flattened, straplike. It's worth keeping an eye on all sorts of plants for this phenomenon.