Thank you all very much for the info' So glad it's not something sinister and that I can leave it to (hopefully) self-seed.
Posts
Doesn't look right for hemlock
I think it might be Ammi visnaga
https://www.sarahraven.com/flowers/seeds/annuals/ammi_visnaga.htm
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
I am 100% sure it is Daucus carota.
See''
https://www.brc.ac.uk/plantatlas/plant/daucus-carota
https://www.first-nature.com/flowers/daucus-carota.php
EDIT..
we posted at same time earlier so you may have missed my answer.