had demonstrated that the same service intervals could be maintained with four fewer trains. The final build of Standard Stock was a small batch of 26 motor cars ordered from Metropolitan-Cammell in 1934, after the formation of the London Passenger Transport Board in the previous year. The Piccadilly line was extended from South Harrow to Uxbridge, and this required an extra eight seven-car trains. These were made up from the new motor cars and some reshuffling of stock between other lines. Although very similar to the 1931 build, there were some minor differences. The 1931 build had used motors with roller bearings for the first time, and ten of the new motor cars were also fitted with roller bearing axle boxes, to reduce the amount of maintenance required with white metal bearings. With the completion of the 1934 build, the total number of Standard Stock cars was 645 motor cars, 551 trailers and 270 control trailers. Allocation By the time the final cars had been delivered, the standard stock was operating on the Northern, Piccadilly and Bakerloo lines. There were 724 cars on the Northern line, consisting of 336 motor cars, 243 trailers and 145 control trailers. This group comprised all of the cars made in 1923, 1924, 1925 and 1926, supplemented by 62 per cent of the 1927 build by Metropolitan, and 13 of the 1927-built Feltham cars. The Piccadilly line had 509 cars, comprising some of the 1927 Metropolitan and Feltham batches, most of the 1929 Feltham stock, the experimental 1930 Feltham train, and all of the 1931 and 1934 stock. The Bakerloo line also had some of the 1927 Metropolitan and Feltham batches, four cars from the 1929 Feltham build and the 1930 Metropolitan stock. This was a total of 198 cars, made up of 82 motor cars, 62 trailers and 54 control trailers. To make up the number of trains, an additional 20 trailers and 20 control trailers were needed, and these were cars of 1920 Cammell Laird air-door stock. Between 1935 and 1940, the London Underground benefited from a New Works Programme worth £40 million. This included extensions to the Northern line and the Central line, with delivery of new trains of 1938 Stock beginning in May 1938. The intention was to run the new trains on the Northern line, and transfer the displaced Standard Stock to the Central line, which was using stock built