Commission, which built the locks at Iffley and Sandford below Oxford in 1633 and at Swift Ditch near Abingdon. In 1751, the Thames Navigation Commissioners were established and built eight locks between Shiplake Lock and Boulters lock between 1770 and 1773. The opening of the Thames and Severn Canal from Lechlade in 1789 led to the building of many of the locks upstream of Shiplake. The six locks built by the City of London Corporation on the tidal section below Staines between 1811 and 1815 required individual Acts of Parliament, and the Thames Conservancy took over their management from the City in 1857. In 1866 the Thames Conservancy became responsible for all river management and installed more locks over the years, the last being Eynsham and King’s in 1928. In 1908 an Act transferred responsibility for the Thames from a point below Teddington Lock to the Port of London Authority, and this included Richmond Lock. The Thames Conservancy was subsumed into the Thames Water Authority in 1974. With the privatization of water supply in 1990 the river management functions passed to the new National Rivers Authority and in 1996 to the Environment Agency. Only Richmond Lock remains under the jurisdiction of the Port of London Authority. Operation Management From the head of navigation at Cricklade to the start of the tidal section at Teddington Lock, the river is managed by the Environment Agency, which has the twin responsibilities of managing the flow of water to control flooding and provide navigable water depths and also regulating and promoting navigation on the river. As a result, all the locks and weirs on the river, except the semi-tidal Richmond Lock, are owned and operated by the Environment Agency. Richmond Lock is managed by the Port of London Authority. Most of the Environment Agency's locks and weirs are staffed by a lock keeper, who often lives in a house adjacent to the lock. The lock keeper's duties involve both operating the lock, and managing the river levels above the lock by adjusting the weir openings. Locks Most locks are operated by their keepers between 9 a.m. and 7 p.m. from June to August, with progressively shorter hours as the hours of daylight reduce, and they are not operated during the lock-keeper's lunch hour between 1 p.m. and 2 p.m. During the summer months Assistant Lock Keepers and volunteers are employed to deal with the