The Bytham River was one of the great Pleistocene rivers of central and eastern England until it was destroyed by the advancing ice sheets of the Anglian Glaciation around 450,000 years ago. The river is named after Castle Bytham in Lincolnshire, where the watercourse crossed the Lincolnshire limestone hills in a valley now buried by Anglian till. West of that location, its catchment area included much of Warwickshire, Leicestershire and Derbyshire. East of that location, the Bytham flowed across what is now the Fen Basin to Shouldham, then southward to Mildenhall, then eastward across East Anglia. It met the Proto-Thames in a delta near what is now the Norfolk/Suffolk border and flowed into the North Sea. Britain was then joined to the Continent by a land bridge and the Bytham joined the North Sea somewhere beyond the northern end of that land bridge.