British Rail Class 458

South West Trains began operating the South Western franchise in February 1996, having inherited all of its rolling stock from British Rail. While this included a small number of trains built in the late 1980s and a larger number of suburban units delivered between 1982 and 1985, a significant proportion of the overall fleet was formed by much older slam-door First Generation EMUs, such as Classes and . In order to begin replacing these older units, SWT issued in November 1996 a request for tenders to supply 30 new air-conditioned four-car EMUs, and in 1997 together with rolling stock lessor Porterbrook awarded to Alstom a £90 million contract for their delivery. All 30 units, numbered 458001–458030, were fitted out at the former Metro-Cammell works at Washwood Heath in Birmingham, which Alstom had acquired in 1989, with the bodyshells being built in Barcelona, Spain. Each unit was formed of two motor cars with driver's cabs, an intermediate trailer car, and an intermediate motor car. Both driving cars had small sections of first-class seating, while the intermediate cars were all standard class. The trailer car was provided with a pantograph well and space for an alternating-current transformer, enabling conversion to overhead-line operation if required at a later date. One bogie on each motor car was fitted with traction motors, for a total of 6 motors along the train, a maximum speed of , and a cumulative power output of . The first Class 458 passenger service eventually ran on 25 February 2000, but even then only two units (458004 and 458005) were available for use. The last six units eventually arrived by October 2002, but it was another seven months—May 2003—before the entire fleet had entered service. Withdrawal from service (2004) Even after the full complement of units had entered service, reliability remained so poor that in January 2004 South West Trains announced that they would withdraw the entire Class 458 fleet at the December 2005 timetable change in readiness to return them to lessor Porterbrook when the lease on the fleet expired in February 2006. At the time of the announcement the trains were only managing an average of between major failures, whereas the new Siemens Desiro () units—which had only entered service in October 2003—were already achieving an average of between faults, and the slam-door fleet had regularly managed intervals of circa . In addition to reliability problems, continued use of the Class 458 fleet was complicated by issues surrounding compliance with the Rail Vehicle Accessibility Regulations (RVAR) 1998. The Regulations, which mandate the accessibility features that vehicle designers and operators need to provide in order to meet the requirements of the Disability Discrimination Act 1995, were in the process of being formulated at the same time as the Class 458 fleet was being designed and the finished units accordingly received temporary exemptions from compliance on a total of 10 different points. The exemption relating to the size of the internal passenger information displays expired on 31 July 2006—having already been extended from 30 September 2004—and the Department for Transport declined to provide any further extension. SWT fitted replacement displays of a compliant size to eight units for use as stand-by stock, while the remainder of the fleet was placed in storage. Return to service In September 2006 the Department for Transport confirmed after a competitive tender process that South West Trains had been awarded a new ten-year contract to operate the South Western franchise, starting in February 2007. As a result of the award, and in keeping with commitments made in its tender, SWT implemented a new rolling-stock plan that called for the withdrawal of its 24 units. Class and 450 units would take over the affected services, and the resulting gaps covered by re-activating the Class 458 fleet. Refresh and reliability improvements Between 2008 and 2010 the fleet was 'refreshed' at Bournemouth Traincare Depot, during which process the units were fitted with CCTV, new seats and tables in first class, and modified RVAR-compliant lavatories and doorway lights. The interiors were also cleaned and repainted. In May 2010, SWT enabled regenerative braking on two Class 458 units as part of trial testing its potential use across both the Coradia Juniper and Desiro fleets. The trials were successful and regenerative braking was enabled across all 30 Class 458 units by mid-2011. By the end of 2012 the fleet was achieving an average distance of between significant failures; making it the most reliable fleet in Britain and the first to achieve 6-figure mileages. The feat was recognised with a Modern Railways magazine Golden Spanner award in the New Generation EMU category on 23 November 2012. Withdrawal from service (2026) On 23 April 2026 South Western Railway announced that it plans to withdraw its Class 458 fleet once enough of the Class 701 Arterio fleet had entered service. ==Conversion to Class 458/5==

South West Trains had experienced a considerable shortage of passenger capacity on many of its suburban routes in the years up to 2012, which it attributed primarily to the fact that passenger numbers had increased dramatically without a corresponding rise in the size of the operator's fleet. As an alternative, Porterbrook proposed to enlarge the Class 458 fleet and reconfigure it for suburban services by using vehicles from the fleet, which Porterbrook also owned and which was at that time being released from service with Gatwick Express. The process, budgeted at £42 million, would allow for all 30 original Class 458 units to be extended by one vehicle, making them into five-car units, after which there would be six five-car Class 460 units left over. These would be comprehensively rebuilt to match the extended Class 458 units, for a total fleet of 36 five-car units that would be designated Class 458/5. The units of this "new" fleet would be used—either individually or in pairs of ten cars—to provide extra peak-time capacity on suburban services into Waterloo from the Hounslow, Weybridge (via Staines), and Windsor lines. A separate improvements package agreed between SWT and Network Rail provided for platform extensions necessary for ten-car operation at over 60 suburban stations, and for the re-opening of one of the four disused platforms at the former Waterloo International terminal. The Department for Transport announced in December 2011 that it had accepted the proposal, South West Trains described the project as advancing its aspiration to become a "10-car railway", Together with 18 of the intermediate cars from the Class 460 vehicles, these became the six "new" Class 458/5 units. The remaining 30 Class 460 cars were prepared for insertion into the Class 458/0s. Additional modifications included re-gearing the traction motors to reduce the train's maximum speed from to , both to reduce the likelihood of overheating when making frequent stops and starts, and because the higher speed was unnecessary on suburban services. Following testing and staff training, entry into passenger service was achieved in March 2014. ==Conversion to Class 458/4==

The South Western franchise was transferred from South West Trains to South Western Railway (a FirstGroup/MTR joint venture) in August 2017. Prior to commencing operations, SWR had taken advantage of low finance costs to order from Bombardier Transportation a new fleet of 750 vehicles—now designated —that would replace Classes , , 458, and on South Western suburban services from late 2019 onwards. However, continuing delays to the Class 701 programme kept all four older fleets in use into the 2020s. South Western Railway had plans to use refurbished units for long-distance services to and from London on the Portsmouth Direct line. However, in March 2021, the operator announced its decision to abandon these plans, citing continuing technical difficulties and future problems complying with accessibility regulations. To make up for the shortfall, 28 Class 458 units have been refurbished and were planned to be redeployed in their place. The reconfigured units will be leased from Porterbrook until 2027 at the earliest and are maintained at Bournemouth Traction and Rolling Stock Maintenance Depot. The first two units to be sent for refurbishment, 458507 and 458517, arrived at Widnes by mid-August 2022. Testing for the 458/4s began on 9 October 2023. In early 2024 it was announced that the plan to use the Class 458/4s on Portsmouth services had been dropped. Later in May 2024, it was announced that the Class 458/4s would instead be used on some limited outer suburban services from London Waterloo. The first Class 458/4 entered service on 24 June 2024, Scrapping of the redundant ex-Class 460 vehicles started in January 2025. The 8 unconverted 458/5s were all withdrawn by March 2026. ==Incidents==

• On 30 January 2015, a small explosion occurred underneath a driving vehicle of unit 458501 near Windsor & Eton Riverside station. The Rail Accident Investigation Branch determined that this was caused by a join between three underfloor power cables not being secured correctly when the unit was rebuilt in 2014. • On 21 December 2019, unit 458519 was involved in a collision with a car between Wokingham and Bracknell. Nobody was seriously injured. ==Fleet details==