To the east of the canal entrance, behind a viaduct arch is the octagonal tower of a hydraulic accumulator, 1869, replacing an earlier and pioneering structure dating from the 1850s by William George Armstrong, engineer and inventor. This regulated the hydraulic pressure of the extensive network of hydraulic mains around the basin supplying the coal-handling machinery. The associated steam raising plant and hydraulic pumps have been removed. The building was converted by Dransfield Owens de Silva for the London Docklands Development Corporation to function as a viewing platform. It (and the basin itself) is now owned by the British Waterways Board; and is a Grade II listed building, and is open every year during Open House Weekend, usually the third weekend in September.