<Tr> <Td> End of Thames Estuary--North Sea (the few settlements further along the debatable estuary to the two points mentioned in the routemap are on inlets or far inland) </Td> <Td> <Table> <Tr> <Td> </Td> </Tr> </Table> </Td> <Td_colspan="2"> </Td> </Tr> <Table> <Tr> <Td> </Td> </Tr> </Table> <P> The River Thames (/ tɛmz / (listen) TEMZ) is a river that flows through southern England, most notably through London . At 215 miles (346 km), it is the longest river entirely in England and the second longest in the United Kingdom, after the River Severn . It also flows through Oxford (where it is called Isis), Reading, Henley - on - Thames and Windsor . The lower reaches of the river are called the Tideway, derived from its long tidal reach up to Teddington Lock . It rises at Thames Head in Gloucestershire, and flows into the North Sea via the Thames Estuary . The Thames drains the whole of Greater London . </P> <P> Its tidal section, reaching up to Teddington Lock, includes most of its London stretch and has a rise and fall of 7 metres (23 ft). Running through some of the driest parts of mainland Britain and heavily abstracted for drinking water, the Thames' discharge is low considering its length and breadth: the Severn has a discharge almost twice as large on average despite having a smaller drainage basin . In Scotland, the Tay achieves more than double the average discharge from a drainage basin that is 60% smaller . </P>

Where does the river thames stop being tidal