Sutton and Mole Valley lines via Epsom and Dorking (including the Bookham Branch) is known to commuters as the "Mole Valley Line" – seven out of the 15 stations are in the Surrey district of Mole Valley. The full title "Sutton and Mole Valley Lines" is used for the lines north of Epsom via Sutton. Confusingly, all Southern services that terminate or call at Sutton are branded as "Sutton and Mole Valley Line" services. The lines which form the route include (in order of construction): None of the lines leads directly to a London terminus, but services use the South Western Main Line to access
River Mole is thought to have merged with the River Wey near Byfleet and then flowed in a north-easterly direction via Richmond to meet the proto-Thames near Ware in Hertfordshire, (today the Mole and Wey are less than apart at their closest point near Painshill Park). During the Middle Pleistocene period, a large ice sheet built up across much of the East of England, reaching as far south as St Albans and Chelmsford, blocking the path of the proto-Thames. Glacial meltwater from the Anglian ice sheet, caused the Thames to divert southwards and flood the valley of the Mole–Wey river, thus adopting