The London Underground F Stock was built in 1920 and 1921 for the District Railway by the Metropolitan Carriage, Wagon and Finance Company. They were partly funded by the government as part of an initiative to help British industry recover from World War I. One hundred steel-bodied cars were built: 40 driving motors, 12 control trailers and 48 trailers with the first train entering service on 23 December 1920. The cars were built with manually operated sliding doors.