Some nice bits of innovation there: secondary coat of camouflage using corrugated sheets as a former?
It looked like that the rough concrete had been overlaid on the original structure. much of it has fallen off. Possibly looks like sheeting ( photo of the last piece of corrugated sheet left) was added before the rough concrete. Im not sure if this was original or post war attempting to seal the structure It was good to be able to get inside a pillbox and view outwards.
What - no heron sitting on top - you are slipping sir Bet the smell was nice once inside Did you find any WW2 plastic or was it all modern day TD
I believe this may have been a mine-watching post - Looking out for parachute mines dropped during air-raids on the approch to london's docklands.