Their task was to remove London's sludge waste from Beckton and Crossness for disposal on the ebb tide at sea, at Black Deep, an extremely deep part of the North sea located fifteen miles off Foulness, on one of the main approaches to the Thames Estuary.
Beckton was one of the Manchester School of philately which advocated the scientific study of all aspects of stamp production including paper, watermark, printing and perforation.