the war more trains were needed. With limited resources, 89 cars to the same design as the 1938 Stock (1949 Stock) were ordered and the pre-war streamlined prototypes were rebuilt. These were introduced on the Piccadilly line, releasing some Standard Stock to augment the trains on the Central line. Three prototype aluminium-bodied seven-car trains were ordered in 1956, to be followed by 76 × 7-car trains of 1959 Stock. It was planned that these would be introduced on the Piccadilly line, allowing the later Standard Stock cars to be transferred to the Central line. However the Central line's Standard Stock was proving troublesome and the trains were diverted to replace these trains, augmented with an extra car. A follow on order of 1962 Stock, as it became known, entered service on the Central line, releasing the 1959 Stock for the Piccadilly line. Standard Stock was withdrawn from the Central line in 1963 and Piccadilly line in 1964. Building the Victoria line had been recommended in a 1949 report, as it would reduce congestion on other lines. New trains were needed for the new line, and eight-car trains made up from two four-car units with two driving motors and two trailers were ordered in 1964. Trials of automatic train operation (ATO) were carried out on the District line in 1962–63, followed by longer term operation on the Central line on a shuttle service between Woodford and Hainault. Successful, the Victoria line was equipped with its 1967 Stock , and as the new trains arrived they spent three weeks working between Woodford and Hainault. The line opened to Victoria in stages in 1968–69 and extended to Brixton in 1971. In the 1970s, the Piccadilly line was extended to Heathrow Airport. The Jubilee line was built under central London, taking over the Bakerloo line's Stanmore branch at Baker Street. The isolated Northern City line was connected with the suburban railway at Finsbury Park. The Standard Stock trains had been replaced by 1938 Stock in 1966, and they last ran in the tunnels in 1975. A through main line service started in 1976 and the line transferred to British Rail. A new fleet of trains was to be built for the Piccadilly line, and its 1956–59 Stock was to replace the 1938 Stock trains elsewhere on the system. However, in 1970 the service on the Northern line was poor, with up to 40 services