MPX5099462: Port of London Authority Dredger Number 10 with barges alongside it at work in high water on the lower reaches of the River Thames. Its main purpose is to keep a shipping channel in the Thames at a depth of 40 feet and 1000 yards across, filling approximately 60 barges each week with roughly 6000 cubic yards of ballast. 27th April 1949 / Bridgeman Images