Lythrum salicaria at a guess. Purple Loosestrife

looks like it from the leaf shape too.

it seeds very freely.

Wonderful colour!

Thanks Owd, I appreciate your feedback. My neighbour has a few things growing wild and that have seeded from elsewhere. His buddleia is very tall, gorgeous colour too...seeded from elsewhere. It all looks pretty OK from our side, thankfully.

Thanks to you to, Eileen.

It was its colour that caught my eye. Sheila. It looks like it's seeded around his other shrubbery.

Wonderful long- lived plant, likes damp conditions. On my list for next Spring!

I may have to discreetly gather some, Sheila! I don't think he'd notice, he's let his front garden grow wild. 😊