Himalayan Balsam

There seems to have been a rapid expansion in the places close to the river where the Balsam has been expanding year on year with it now covering a large area. Some individual plants are well over 2 metres ( that's six feet in old money) see extra for flowers well above my head. I suspect these plants have benefitted from the very wet conditions over the last 9 months in the same way that established shrubs in gardens have put on growth spurts.