VC - I take that back.
Just been looking up “filipendula” after your suggestion and I think it’s Filipendula Palmata.
I guessed it was something j had bought sometime rather that a “weed” like meadowsweet because I’d gone to the trouble of weeding around it.
Can you do the honours for me, please and edit the title so it shows what I think it is!!
Thanks for your suggestion!