The British Rail Class 40 is a type of railway diesel-electric locomotive. A total of 200 were built by English Electric between 1958 and 1962, numbered D200-D399. Despite their initial success, by the time the last examples were entering service, they were already being replaced on some top-level duties by more powerful locomotives. As they were slowly relegated from express passenger use, the type found work on secondary passenger and freight services which they hauled for many years. The final locomotives ended regular service in 1985. The locomotives were commonly known as "Whistlers" because of the distinctive noise made by their turbochargers.
Origins
The origins of the Class 40 fleet lay in the prototype diesel locomotives LMS No. 10000 and 10001, ordered by the London, Midland and Scottish Railway; Class D16/2, ordered by British Railways between 1947 and 1954); and, most notably, with the Southern Region locomotive no. 10203, which was powered by English Electric's 16SVT MkII engine, developing 2,000 bhp (1,460 kW). The bogie design and power train of 10203 was used almost unchanged on the first ten production Class 40s.
Prototypes
thumb|left|One of the prototype locomotives, D205, on the Great Eastern Main Line in 1963
British Railways originally ordered ten Class 40s, then known as English Electric Type 4s, as evaluation prototypes. They were built at the Vulcan Foundry in Newton-le-Willows, Lancashire. The first locomotive, D200, was delivered to Stratford Works on 14 March 1958. Following fitter and crew training, D200 made its passenger début on an express train from to on 18 April 1958. preferring to hold on until the Class 55 "Deltics" were delivered.
The London Midland Region was only too pleased, as the Eastern Region's decision released additional locomotives to replace their ageing steam fleet. The West Coast Main Line had been starved of investment for many years and the poor track and generally lower speeds (when compared to the East Coast route) suited Class 40s, as the need to hold trains at speed for long periods simply did not exist and it better took advantage of their fairly rapid acceleration.
Production
thumb|right|D236 with [[Merseyside Express at Crewe, in BR green with no warning panels (April 1960)]]
thumb|English Electric no. 40125 (ex-D325) in a badly faded BR green with all yellow front ends, gangway doors and split headcode panels at Shrewsbury General (May 1975, scanned slide)
Following the mixed success of the prototypes, another 190 locomotives were ordered by British Railways and were numbered from D210 to D399. All were built at Vulcan Foundry, except one batch of twenty (nos. D305–D324) which were built at Robert Stephenson and Hawthorns factory in Darlington. All the locomotives were painted in British Railways' diesel green livery and the final locomotive, D399, was delivered in September 1962.
Batches of the class were built with significant design differences, due to changes in railway working practices. The first 125 locomotives, nos. D200–D324, were built with steam-age 'disc' headcode markers, which were used to identify services. Later, it was decided that locomotives should display the four character train reporting number (or headcode) of the service they were hauling; nos. D325–D344 were built with 'split' headcode boxes,
From 1973, locomotives were renumbered to suit the TOPS computer operating system and became known as Class 40. D201 to D399 were renumbered in sequence into the range 40001 to 40199. The first built locomotive, D200, was renumbered 40122; vacated by the scrapping of D322, following accident damage.
Named locomotives
thumb|right|D213's Andania nameplate, preservation-era image
Locomotives in the range D210–D235 were to be named after ships operated by the companies Cunard Line, Elder Dempster Lines and Canadian Pacific Steamships, as they hauled express trains to Liverpool, the home port of these companies. The only locomotive not to carry a name was D226, which was to carry the name Media but never did so. From approximately 1970, with Class 40s no longer working these trains, the nameplates were gradually removed, However, the Ian Allan Motive Power Combined Volume (a list of all operational locomotives published annually for enthusiasts) was still listing the names of all officially named Class 40 locomotives in 1980, despite none having carried their nameplates for many years.
{|class="wikitable sortable collapsible"
|+
!Loco!!Name!!Shipping line || Date named
|-
| D210 || || Canadian Pacific Steamships ||
|-
| D211 || Mauretania || Cunard Line ||
|-
| D212 || Aureol || Elder Dempster Lines ||