I was going to say maybe a Dropmore? I have a blue version of Dropmore, but I know a deep pink version exists.
I live in west central Scotland - not where that photo is...
When you don't even know who's in the team
Its a Persicaria.
Were you thinking of Lythrum virgatum Dropmore Purple?see my 1st pic
Cos that is not the mystery plant.
Mystery plant is Persicaria as mentioned by others.
maybe Persicaria affinis...see 2nd pic