Greater Manchester spans 493 square miles (1,277 km2), which roughly covers the territory of the Greater Manchester Built-up Area, the second most populous urban area in the UK. It is landlocked and borders Cheshire (to the south-west and south), Derbyshire (to the south-east), West Yorkshire (to the north-east), Lancashire (to the north) and Merseyside (to the west). There is a mix of high-density urban areas, suburbs, semi-rural and rural locations in Greater Manchester, but land use is mostly urban—the product of concentric urbanisation and industrialisation which occurred mostly during the 19th century when the region flourished as the global centre of the cotton industry. It has a focused central business district, formed by Manchester city centre and the adjoining parts of Salford and Trafford, but Greater Manchester is also a polycentric county with ten metropolitan districts, each of which has at least one major town centre and outlying suburbs.
Trafford has a strong economy with low levels of unemployment, and, apart from the City of Manchester, Trafford is the only borough to be above the national average for weekly income. Socially, the area is middle class and contains commuter towns. Altrincham and Sale West is the only parliamentary constituency in Greater Manchester to be held by the Conservative Party. Trafford has the best record for education in Greater Manchester.
During the Second World War Turing worked at Bletchley Park, the UK's codebreaking centre, and was for a time head of Hut 8, the section responsible for German naval cryptanalysis. He devised a number of techniques for breaking German ciphers, including the method of the bombe, an electromechanical machine that could find settings for the Enigma machine.