Staines-upon-Thames (until May 20, 2012 Staines) is an English middle town with 52,400 inhabitants (2001) in Greater London within the M25 motorway ring and close to Heathrow Airport. Staines belongs to the county of Surrey and the Borough of Spelthorne. The city is located about 30 km west of Central London on the Thames. The River Colne flows west of the city into the Thames and the River Ash flows in the north of the city.