Originally conceived as a cheaper and more reliable alternative to the Advanced Passenger Train in the early 1970s, the British Railways Board authorised the development of a prototype High Speed Diesel Train with two locomotives designated as Class 41. These aerodynamic power cars were constructed by BREL at their Crewe Works and outshopped in June and August 1972, fitted with Paxman “Valenta” 12RP200L engines which developed 2,250 hp. After a short period, the Mk.3 passenger cars from BREL’s Derby Litchurch Lane Works completed the prototype set, which then became British Rail Class 252.
The power cars, having initially been numbered 41001 and 41002, were later given the coaching stock numbers 43000 and 43001 for operating trials on the Eastern Region and subsequent transfer to the Western Region. This prototype InterCity 125 clinched the world record for traction of 143mph (230kmh) on June 12, 1973.Following evaluation of this prototype design and a change of name to High Speed Train, British Rail placed orders for similar trains for use on the Western, Eastern, Scottish and London Midland Regions.When originally built at BREL Crewe Works, the InterCity 125 units were considered to be diesel multiple units and allocated as Class 253 to the Western Region and Class 254 for the Eastern Region, as it was envisaged that the sets would remain in fixed formation.
Those original HST’s consisted of a Driving Motor Brake (DMB), Trailer Firsts (TF), Trailer Seconds (TS), Trailer Restaurant Unclassified Kitchen (TRUK) and a Trailer Restaurant Second Buffet (TRSB). Once the Trailer Guard Second (TGS) were introduced, the later power cars had no guard’s equipment installed. By 1987 most power cars were simply classified as Driving Motor (DM), although they still had luggage van space, retaining a window by the luggage door on each side.Following problems with the power cars and the operational ease of removing power cars to perform scheduled maintenance, unit formations were abandoned and from then on, HSTs were considered to be formed of two power cars with a rake of Mk3 carriages in between, resulting in the Class 43 locomotive prefix being adopted.
The 197 Class 43 power cars produced between 1976 and 1982 were numbered 43002 to 43198 and are officially the fastest diesel units in the World. The units have an absolute maximum speed of 148mph (238kph), which is the current world diesel traction record, set on November 1, 1987. The top speed of the HSTs during regular service is 125mph (200kph). Prior to the introduction of HSTs, British trains were limited to a maximum speed of 100mph (160kph). The increased speed and rapid acceleration/deceleration of the Class 43 locomotives made them ideal for passenger use and journey times around the country were slashed. Class 43 driven services replaced stock on the West Coast Main Line, East Coast Main Line and later the Midland Main Line, although it was not always possible to operate to their full potential.
In 1987, for trial purposes, 8 Class 43s were converted for use as Driving Vehicles with the Class 89 and Class 91 locomotives. The power cars were fitted with buffers and Time Division Multiplex (TDM) equipment that allowed them to directly control the other locomotive. Following the delivery of Mk4 stock, the TDM equipment was removed and the power cars reverted to their normal duties. During the late 1990s, 25 Class 43s were re-engined with Paxman 12VP185L engines in an attempt to reduce fuel consumption and emissions; however these proved to be less reliable in service than was hoped.
In 2007 Brush Traction and Hitachi Limited equipped Paxman “Valenta” powered 43089 and semi-permanently coupled Mk3 coach with a diesel-battery hybrid power system for trials with Network Rail’s New Measurement Trains.
The HST fleet has seen several changes to the operating companies since privatisation in 1993, former operators including Midland Mainline, Virgin, Cotswold Rail, Cross Country and Great North Eastern Railway. Class 43 driven sets continue to operate nationwide, courtesy of First Great Western, East Coast, East Midlands Trains, Grand Central, Cross-Country and Network Rail.
At the beginning of April 2006, FirstGroup, having secured the newly combined FGW franchise, unveiled a proposed new livery with a graduated blue to purple body colour and horizontal dynamic lines. Originally applied to both coaching stock and power cars, upon refurbishment the power cars received a modified livery of solid blue/purple, minus the dynamic lines. Unit 43070 was delivered to traffic on November 19, 1977 and became The Corps of Royal Electrical and Mechanical Engineers on October 16, 2007. Here it is paired with Unit 43036 which is a year older, being delivered to traffic on November 20, 1976.