That is rosebay willowherb. a good native for many moth and butterfly larvae.
scientific name Chamaenerion angustifolium. common names include fireweed. it is often found growing along railway lines as the fluffy seeds are easily 'transported' in the air turbulence as a train passes.

Thank you

This seems to have done better than any other 'weed' here in the Chilterns this summer, its blooms are very pretty but I have been trying to weed it out of the garden before it goes to seed, it produces so much! That said, even its seeds are attractive, each like a tiny feather ...... it isn't a gardener's bane like bindweed or ground elder but it would soon dominate the garden if left undisturbed.

Love the picture with the black & white background and brightly coloured flower. Was that intentional?

Yes Amsterdam I’ve have indulged in a little free licence with paint shop pro.

Great. Very effective. Love it!