This is Indian Balsam or Himalayan Balsam (Impatiens glandulifera) photographed next to the River Annan at Hoddam, Dumfriesshire, Scotland.
Introduced to the UK in 1839, it is now a troublesome, invasive species, most commonly found along waterways and on waste ground. The photograph below shows an example of the problem along this river. The RHS suggest ways to erradicate it here.
