This was part of the drainage system that kept the south bank free from flooding. The ground being very close to river level it was necessary to have a gate, or sluice-gate, across the drainage pipe as it entered the Thames so that at high tide the water did not flow from the river up the pipe or channel onto the land. So the outlets became known as sluices. there were others on the south bank: Heathwall, Earl, Salisbury Lane. An extensive system.
The National Archive holds plans showing the extensive drainage system that connected to the Duffield Sluice: Main sewer from Duffield Sluice near Cherry Garden, Rotherhithe to the dead head near Lambeth Palace; Duffield Sewer from the west end of Spa Road to its outlet at Duffield Sluice; Duffield sluice {we think they mean ‘sewer’} from the place it takes the water near Lambeth Palace to where it empties itself at Bermondsey Wall; Duffield Sewer from the Bricklayers Arms to Star Corner and to the west end of Spa Road.
