This connects the maintained level and tidal sections of the Bow Back Rivers. The photo shows the old gates (since replaced by stop-planks) at the tidal end. Two sets of gates were provided so that the lock was usable whether the tide was higher or lower than that on what was then the semi-tidal section. There is no evidence that the lock was ever used, except for a few passages by enthusiasts in the 1960s and 70s. It was built as a replacement for Marshgate Lane flood gates, under the River Lea Flood Prevention Act (1930), by which time commercial traffic on the southern half of the Back Rivers was next to nothing.