The Maunsell Forts in the Thames taken in October 1976 on Kodachrome film.
I believe this picture was taken from the ferry Olau Kent on it's journey from Sherrness in Kent to Vlissingen in Holland by a traveller on board that vessel. This is one of a number of pictures which were taken on that trip, which will be posted on Found-Film over the course of the next few days.