and to use either electric or mechanical transmission. The first twelve cars were transferred from Ruislip Depot to Wimbledon in August 1964, from where they were moved to Micheldever sidings. Further cars followed in June 1965. In October, a plan to electrify the line was announced, and the idea of fitting diesel engines was dropped. In 1966, the Southern Region had 44 cars at Micheldever, and London Transport had 29 more which were set aside for the scheme. 10 of the Micheldever cars were scrapped, and 12 more were obtained from London Transport. Overhaul of the electrical and braking systems was done at Acton Works, which involved transferring the cars from Micheldever back to London Transport. This included conversion to work with a three-rail system, rather than the standard London Transport four-rail system. The number of cars to be shipped to the Isle of Wight was reduced from 46 to 43 because of the cost of this work. After overhaul, the cars were transferred to Stewarts Lane, where they were repainted in British Rail blue, and were then taken to the Isle of Wight. They were loaded onto a road vehicle at Fratton belonging to the haulage company Pickfords, and crossed to the island on the Portsmouth to Fishbourne ferry. Care was needed to ensure that the weather and tides were suitable, and motor cars had to be transferred on special sailings, rather than regular crossings, because of the difficulty of unloading a vehicle of this weight without damaging the ship's unloading ramp. The cars were formed into 4-car and 3-car units, initially designated as 4-VEC and 3-TIS units. They became Classes 452 and 451. They were later reclassified to become Classes 485 and 486. Apart from those cut up following accidents at Ryde depot, and other early withdrawals, most of these units were withdrawn between 1988 and 1991, when they were replaced by London Underground 1938 Stock. In October 1990, five cars were returned to London Transport, to form a Heritage Train. They worked under their own power between Fratton and Wimbledon, and were displayed at an open day at Morden Depot, celebrating 100 years of the Northern line. Manufacturers Standard Stock is used to describe six experimental cars built by five manufacturers in 1923, and 18 batches of production cars, totalling 1460 vehicles, built by six manufacturers between 1923 and 1934. It became the most prolific class of