the earlier designs. In 1920 the District took delivery of new cars, incompatible with the existing fleet, with three hand-operated double sliding doors on each side. In 1923 fifty motor car bodies were ordered to allow some of the original 1904–05 car bodies to be scrapped. From 1926 two stock pools were created. Main line trains were formed from 101 new motor cars supplemented by motor cars rebuilt from the steel bodied cars originally constructed in 1910–14 and 1923, and trailers modified from the original wooden bodied cars. A small pool of unmodified 'local stock' worked the shuttles from Acton Town to South Acton, South Harrow and Hounslow. In 1932 the line to Upminster was electrified and new vehicles were purchased. After the District Railway became part of London Underground, similar cars were ordered to allow the Metropolitan line be extended to Barking and replace some of the rapidly deteriorating original wooden trailers. The 1935–40 New Works Programme fitted electro-pneumatic brakes and air-operated doors to most of the District line stock and allowed the remaining wooden cars to be scrapped. A number of motor cars were not suitable for conversion and so some trains retained their hand-worked doors and these ran until 1957. a driving motor car built in 1923 is a static exhibit at London Transport Museum at Covent Garden. See also London Underground Metropolitan Railway District line Circle line Metropolitan line Hammersmith & City line Piccadilly line Notes and references Notes References Bibliography Snippet view at google.com, retrieved 20 August 2012 Snippet view at google.com, retrieved 20 August 2012 Other publications External links District Line Clive's UndergrounD Line Guides Etching of the "Works of the Metropolitan District Railway on the Thames Embankment at Westminster" published in Illustrated London News. Available from flickr accessed 8 June 2012 Print dated 1866–67 of "The construction of the Metropolitan District Railway" near South Kensington. Available from Museum of London, accessed 8 June 2012 Painting by Jack Hill of a District Railway and a GNR steam trains at Farringdon. Basilica Fields (blog), accessed 8 June 2012 Predecessor companies of the London Underground Railway companies established in 1864 Railway companies disestablished in 1933 Transport in the London Borough of Barking and Dagenham Transport in Berkshire Transport in the London Borough of Brent Transport in the City of London Transport in the London Borough of Ealing Transport in Essex Transport in the London Borough of