The Hogsmill River in Surrey and Greater London, England is a small chalk stream tributary of the River Thames. It rises in Ewell and flows into the Thames at Kingston upon Thames on the lowest non-tidal reach, that above Teddington Lock. The river is long and has a catchment area of about . Nearby land was formerly flood-meadows; following improvements it is now mostly sports grounds, a sewage treatment works and green space, save for Kingston and Epsom town centres. It is a habitat of many animals, fish and insects. The 12th-century Clattern Bridge, one of the oldest road bridges in England, crosses the river in the southwest of Kingston town centre. The Coronation Stone, now sited close to the river in Kingston, is believed to have been used for the coronation of Saxon kings in the 10th century. It was used as a horse mounting block until 1850 when it was mounted on a plinth in the town centre. The river has five tributaries: Green Lanes Stream, Ewell Court Stream, Horton Stream, Bonesgate Stream and Tolworth Brook. Course of the river Epsom and Ewell The source of the Hogsmill River is a chalk spring just outside Bourne Hall Park in Ewell, Surrey. It flows in a northerly direction between Kingston Road and the sports field beside the railway track. The river passes the sites of the Lower and Upper Mills, and Ewell Court Mills, where gunpowder was produced in the 18th and 19th centuries, and gently bends to the left before flowing under the Mole Valley railway line between and at the start of the Hogsmill Open Space which follows the river until the borough boundary with Kingston. The river continues its course in green space between the residential areas of Ewell Court and West Ewell and is joined by the Green Lanes Stream. After a short distance of green space, the river runs as a boundary between Poole Road Recreation Ground and Ewell Court Park and flows behind Ewell Athletics Track. It reaches another confluence, this one being with the Ewell Court Stream, flowing in just downstream from Ewell Court Lake as it continues into West Ewell. The river runs further through the open space and passes near West Ewell Infants School and Ruxley Church before flowing under Ruxley Farm Bridge, the site of the former Ruxley Splash. It passes Riverview Primary School in the residential area of