London Underground A60 and A62 Stock

The design was formulated by W. S. Graff-Baker of the London Passenger Transport Board, as part of the electrification of the Metropolitan line from Rickmansworth to Amersham and Chesham under the 1935–1940 New Works Programme.^[7]

Initial plans for a new Metropolitan line fleet proposed 23 eight-car trains to be reformed from the later builds of T Stock in February 1939 by equipping them with air-worked doors, but the start of the Second World War brought the whole scheme to a halt.^[8]

Upon revisiting the plans in 1944, construction began on a test car shell, numbered 17000, at Acton Works with features later incorporated into the production fleet, notably the wide body profile and three air-operated sliding double-doorways which were worked by an additional guard in the adjacent coupled coach.^[8] As a compromise between efficient practices of slam-door stock and increased room and safety of sliding-door trains, the interior layout featured an unusual central seating aisle with corridors on both sides and a central partition.^[9] Overall, the prototype car was mounted on a T Stock trailer underframe and District line type K2 bogies and was painted in London Transport red livery.

Trailer car 17000 was put into service in January 1946, coupled within a T Stock unit.^[8] Public reaction was negative, owing to the seats not being abutted to any windows with the side corridors present alongside little protection from the weather as the doors opened adjacent to the seats.^[10] Following on from this feedback, a second prototype car of a similar profile (numbered 20000) was constructed and entered service in June 1947, this time with two double-doorways, a central corridor and pairs of side seats. 17000 had its interior rebuilt to match 20000 in November 1949 and was renumbered 17001. The two trailer cars remained permanently coupled until their withdrawal from service in 1953.^[9]

A mock-up driving motor car was also constructed at Acton Works in 1950 based on the prototype T Stock cars. It featured circular windows and a rounder body profile, matching that of the 1938 Stock.^[8][11][12]

With electrification recommencing in 1959, London Transport placed an order with Cravens of Sheffield for 31 four-car trains to replace both T Stock on services to Watford and Rickmansworth, and locomotive-hauled services to destinations north of Rickmansworth. These trains were designated as A Stock to mark the electrification of the Metropolitan line to Amersham. As such, the earlier batch were referred as the A60 Stock. The first units, 5004 and 5008, entered service to Watford in June 1961.^[3][4][5] London Transport later ordered an additional 27 A62 Stock trains; these were introduced between 1961 and 1963 to replace F and P Stocks on the Uxbridge branch. By December 1963, the roll-out was complete.^[13]

Four-car units were also used on the East London line (initially a branch of the Metropolitan line) from 1977 until 2007, when the line closed to become part of the London Overground network,^[13] trains traversing empty between New Cross and Neasden Depot.

To avoid hauling under-utilised carriages, eight-car trains were divided into their component four-car units at the end of the peak hours, with one unit often stabled. At the start of the peak hours, single units would be coupled to create a longer train. Although this practice was discontinued across the Underground network upon the A Stock's introduction, the unique nature of the Metropolitan line prolonged the operation. From June 1962, decouplings were scheduled at Uxbridge, Watford or Rickmansworth in the platforms, and at Amersham in the sidings.^[14]

The practice was discontinued after the 1980 summer season; with exception for the Chalfont & Latimer–Chesham shuttle and East London line, which always required four-car units anyway; since it had become an operational nuisance, with uncoupling usually being cancelled during the winter as it was hazardous in leaf-fall and icy conditions. This also greatly simplified subsequent rolling stock modifications to equip controls for one person operation (OPO) since the inner car cabs would not need to be converted.^[15] Conversion to OPO took place on the Metropolitan line from 29 September 1986, following modifications to driving cars with new door controls, safety equipment and larger headlights.^[16]

Beginning in 1987, overhauls at Neasden depot saw seven A Stock units having their roofs painted in maroon while a further three were painted in red. Some units had names painted on the cab fronts but this was short-lived due to management objections.^[17] In 1989 two A Stock units were fitted with different interiors and repainted into corporate liveries to gauge public opinion prior to refurbishment of the entire fleet.^[18]

Commencing between 1994 and 1997, the A Stock trains were refurbished by Adtranz at Derby Litchurch Lane Works, which saw new interiors fitted, car end windows installed, new moquette sewn, the corporate livery being applied and suspension improved.^[15][19] At the time of refurbishment, the Metropolitan line had a low priority for receiving new trains.^[20] When built it had a top speed of 70 mph (110 km/h) (world's fastest fourth-rail train), but following refurbishment it was restricted to 50 mph (80 km/h) to improve reliability.

The stock was a compromise between the needs of longer-distance "outer suburban" passengers on the outer reaches of the line and short-distance "urban" passengers over the heavily used Circle and Hammersmith & City lines.

A distinctive feature was the use of transverse seating only, which was uncommon on the Underground, designed for journeys which might last over an hour. Most of the seating was of the high-back 2+3 arrangement.^[15] Other unusual features also included luggage racks and umbrella hooks, despite their presence on most contemporary British mainline trains.^[6]

Four tip-up seats, previously used by guards prior to conversion to one-person operation, were provided at the rear of the driving motor.^[21] Despite each 8-car train seating 448 passengers,^[19] the A Stock retrospectively provided fewer seats than the locomotive-hauled and T Stock trains that they replaced, but more seats than the S Stock which replaced them.

A60 and A62 Stocks were nearly identical in appearance. The most significant differences were the border around the destination window on A62 motor cars and the make of compressor under the trailer cars: A60 stock used the Westinghouse DHC 5A, A62 cars the Reavell TBC 38Z.^[22]

Cars had a four-digit number. The first digit identified the type of car (driver or trailer), the last three digits the set (000 to 231).

In further detail:

^ operational DM
† Renumbered
+ Replaced/formed with a renumbered car

The A Stock fleet reached 50 years of service on 12 June 2011.^[25] The age of the stock made spare parts more difficult to obtain and vehicles had to be cannibalised to keep the rest of the stock in operation.^{[citation needed]}

S8 Stock trains replaced the stock, with the first unit introduced on 31 July 2010.^[26] This is similar to the S7 Stock for the District, Circle and Hammersmith & City lines; the main differences are the layout and number of seats and the provision of two sand hoppers for each rail due to the different conditions at the country end of the line.^[27] On 9 October 2010, the first eight cars of A Stock were sent for scrap, units 5197 and 5173. Main withdrawals began on 20 January 2011, with units 5006 and 5179 being sent to the CF Booths of Rotherham for scrapping.^[28]

In February 2012, the London Transport Museum began offering luggage racks from withdrawn A Stock for sale.^[29]

The last train ran in passenger service on 26 September 2012, formed of units 5034 and 5062.^[30] The same train was used a few days later on 29 September for a "farewell" railtour organised by the London Transport Museum, running along the entire Metropolitan line. At one point during the railtour, the train was unofficially recorded at 74 mph. One of the driving motor cars, 5034, which was part of the first (as 5008) and also the last A Stock train in service, was earmarked for preservation and was delivered to the London Transport Museum's Acton Depot.^[6]

One A Stock unit (5110-6110-6036-6111-5111) was retained for departmental use as a Rail Adhesion Train until March 2018, giving the fleet a total service span of 57 years. It had been last used in December 2017, when it had developed a fault and repairs were deemed unnecessary as it was planned to be withdrawn and replaced by a former District line D78 Stock unit at the end of the year.

The night of 24 May 2018 was the final time an A Stock unit ran under its own power on the London Underground network, the RAT set working an empty stock movement from Neasden Depot to Ealing Common Depot. The set was subsequently removed from the adjacent Acton Museum Depot by road for disposal on 17-18 July 2018.