a local level, the London Borough of Sutton Council has been run by a Liberal Democrat majority since 1990. Population and demography Most of Sutton, including the town centre, falls under the SM1 postcode area, though places south of Sutton railway station are part of SM2 instead, and the western part of Sutton Common is in SM3. The population of the town, comprising the Sutton Central, Sutton West, Sutton North and Sutton South wards, was 41,483 in the 2011 census. A majority of the town's population is in the middle class ABC1 social group. Geography Geology, soil and elevations Sutton is one of several towns located on a narrow bed of Thanet Sands which extends from Croydon in the east, to Epsom in the west. To the south of this belt is chalk of the North Downs, and to the north is clay. The belt of Thanet sands allowed wells to provide clean water, and this attracted settlements from a very early date. The Sutton and Cheam Water Company began operations in 1864, and by 1900 had built 142 miles of mains. The company merged with the East Surrey Water Company in 1996 to form Sutton and East Surrey Water. Elevations in and around the town range from AOD in Belmont to in Sutton Common, at the start of the Pyl Brook stream. Location Sutton has formed part of Greater London since 1965. "Sutton, Surrey" is often used for addresses in the town, Surrey being the former Postal County (and the historic or traditional county) in which it lies. Royal Mail's Flexible Addressing policy allows this. There is another, much smaller Sutton in Surrey, near Dorking. Sutton mainline railway station is known as "Sutton (Surrey)" by Southern Railway Ltd. Its location is west of Croydon, north-east of Epsom and south-east of Kingston upon Thames. Green spaces In addition to the St Nicholas church grounds, there are two areas of green space within the town centre, Sutton Green and Manor Park. Sutton Green is at the northern end of Sutton High Street, near All Saints Church. It is bordered by a row of detached Victorian villas to the west, the High Street to the east and Bushey Road to the south. The green dates from 1810, when it was awarded to the residents of Sutton under the Sutton Common Enclosure Award. Victoria Gardens, a smaller area of green space which once