British Rail Class 42

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D852 Tenacious at Old Oak Common, 1964

British Railways' (BR) Type 4 "Warship" class diesel-hydraulic locomotives were introduced in 1958. They were divided into two batches: examples built at BR's Swindon works were numbered in the series D800 to D832 and from D866 to D870, had a maximum tractive effort of 52,400 pounds force and are the British Rail Class 42 of this article. 33 others, D833-865, were constructed by the North British Locomotive Company and became British Rail Class 43. They were allocated to Bristol Bath Road, Laira Plymouth, Newton Abbot and Old Oak Common.

The Western Region of British Railways had decided upon hydraulic transmission with lightweight alloy construction for its new diesel locomotives to replace "King" and "Castle" class steam locomotives. This was partly because of the stiff gradients between Exeter and Plymouth on the Paddington-Penzance route: to save fuel compared with hauling the additional weight of the locomotive up these gradients and allow an extra revenue-earning passenger coach to be added to the train. It quickly became apparent that the largest centre of expertise on diesel-hydraulic locomotives was in Germany. The Western Region (in view of post-World War II sensibilities) negotiated a licence with German manufacturers to scale down the German Federal Railway's "V200" design to suit the smaller loading gauge of the British network, and to allow British manufacturers to construct the new design. Two Class 42s are preserved: D821 and D832 are the only survivors.

Mechanical details

Each locomotive was powered by two Maybach 1035 hp (D800-802) or 1135 hp (D803-829, D831-832 and D866-870) MD650 engines coupled to Mekydro hydraulic transmissions. The lower engine rating in the first three was because the first batch of transmissions could not accept more than this; a shortcoming swiftly rectified, although the technology of the time limited hydraulic transmissions to below 2000 hp input, hence the need for two engines. D830 Majestic was equipped with two Paxman YJXL Ventura engines rated at 1200 hp each as a potential showcase of an alternative British engine which might prove superior to the German Maybach. The new locomotives were substantially lighter than previous diesel-electric designs: a Class 44 "Peak" locomotive weighed 138 tons and required 8 axles to carry it; the D800s weighed less than 80 tons and only needed 4 axles. D800-802 were produced as a pilot order and differed slightly both mechanically and cosmetically from the others. Aside from the obvious differences of disc versus rollerblind headcodes and the slightly less powerful engines, D800-802 were only equipped with six power controller notches, which was found to be unsatisfactory for smooth acceleration and economical running in operational use. These differences meant D800-802 were effectively a separate sub-class and could not work in multiple with the others (although the "white diamond" code multiple working capability of the Warships was rarely used until the late 1960s, and was removed from many locomotives as a constant source of electrical problems). In 1960 British Rail introduced the Class 43 diesel hydraulic locomotives, with a maximum tractive effort of 53,400 pounds force. These were constructed by North British Locomotives, numbered in the range D833 to D865 and also bore names. Although of a very similar design to the Swindon-built examples, the 43s were equipped with MAN engines and Voith hydraulic transmissions at the same power rating as the Swindon locomotives. The Maybach engines were a more sophisticated design, with advanced features such as oil-cooled pistons that the MAN design lacked. The German V200 class, upon which the D800 design was based, used MAN and Maybach engines coupled to Mekydro and Voith transmissions in roughly equal proportions, with engines and transmissions being completely interchangeable. Thus one locomotive might have one MAN engine coupled to a Mekydro transmission and a Maybach coupled to a Voith. This interchangeability of engines and transmissions was theoretically a feature of the BR design as well, but was never exploited. Detail differences in the floor construction after the first few Swindon production locomotives removed the ability to exchange transmissions.

Names and liveries

Each locomotive bore a name: for example D825 was Intrepid. All except D800 and D812 were named after Royal Navy vessels. D800 was named Sir Brian Robertson after the Chairman of the British Transport Commission at the time; Robertson was reportedly very concerned that the BTC should not be seen to stifle innovation at Regional levels within BR and this policy was very likely a major boost to the WR's aspirations for a full diesel-hydraulic fleet. D812 was planned to carry the name Despatch but was eventually named Royal Naval Reserve 1859-1959. All except these two bore a subtitle "Warship Class" in smaller letters underneath the main name. A nice touch was that throughout the production series examples (including the NBL-built D833-865) the names were allocated alphabetically. This caused some difficulty when Swindon was unexpectedly given an order for five more locomotives (which became D866-870); a shortage of Warship names beginning with Z required some names for the higher numbered NBL examples to be reallocated. The original livery for all D800s was BR green with a light grey waistband and red bufferbeams. In the mid-1960s the WR decided upon maroon as its new house colour for mainline diesel locomotives, this going very much against standard schemes imposed by BR's overall management. In 1967 the first D800 (D865) appeared in the new BR blue scheme although it was left for some time with maroon skirting. Half yellow nose ends appeared before the end of the green livery and eventually both maroon and blue-liveried locomotives received full yellow ends. Only the earliest withdrawals were never painted blue. After withdrawal of steam in 1968, and as a small money-saving gesture, the "D" prefix was dropped from locomotive running numbers when repaints occurred - so for example, D832 became just 832 as there was now no chance of it conflicting with a steam locomotive number.


The D800s were originally intended for the Paddington-Birmingham route and tests proved that their extra weight and power allowed them to run to a two hour schedule with 368 tons in tow: one coach more than a Class 40 could manage. These plans were put back when Paddington became the temporary London terminus of choice for Birmingham during the early 1960s, whilst BR's preferred route from Euston via Rugby was electrified. Loads of greater than 370 tons would be required and the service remained steam-hauled until the advent of the more powerful "Western" diesel-hydraulic locomotives. The first service route for the class therefore became Paddington-Penzance, either via Swindon and Bristol, or via Newbury and Westbury on the "Berks and Hants" route. This allowed for elimination of steam on the difficult-to-operate railway west of Newton Abbot. In October 1958 D800 became the first locomotive to take up the class' new diagram of the up Cornish Riviera Express (Penzance to Paddington), the 18:30 Paddington-Bristol and the 21:05 Bristol-Plymouth - the last part of the diagram allowing the locomotive to return to the brand new depot at Laira in Plymouth once this was fully operational in 1961.

The maximum speed of the D800 class was officially 90 mph but this could not be rigidly enforced because the transmissions could not be precisely governed. 102 mph was recorded by D801 in private tests during 1959, albeit on a downgrade. The summer of 1959 saw 100 mph service trains diagrammed for D800s with the Paddington-Bristol "Bristolian" set a schedule of 100 minutes. The outward journey was via Bath and required an average speed of 71 mph and the return journey via Badminton averaged at 70.6 mph. For a very brief period the D800s achieved both the schedule and more with D804 exceeding 100 mph three times on one early run from Bristol. This was soon ended when the Western Region's civil engineers imposed a blanket 90 mph maximum speed on all the Region's main lines, where for five years there had, uniquely to BR at the time, been no restrictions at all. The root cause of this worry was the effect of small-diameter powered wheels carrying far more weight per inch of tread than those of a steam locomotive. These concerns arose particularly from experiences in the United States of America although the significant rail damage reported there was mostly caused by wheel sliding under braking with heavy tailing loads which were very unlikely to occur on BR. With the benefit of modern hindsight it is possible that, even though the full US experience would not be replicated, "gauge corner cracking" (the formation of microscopic cracks in the rails that was the primary cause of the Hatfield rail crash of 17 October 2000 in the UK) could have been a possibility if the schedules had been adhered to.

In the event, several D800 drivers began reporting uncomfortable lurching over points or on poorly-maintained track at high speeds around this time. The problem was eventually traced to the novel design of the bogies and their means of attachment to the locomotive bodyshell: it had given the German V200s no trouble because of the system-wide 75 mph speed limit on the German Federal Railway at the time. High speed running magnified the effect of the almost rigid link between body and bogie, and oscillations created in the entire locomotive structure when the wheels hit pointwork or indifferent track made derailment a very real risk as the tyres on the wheels wore down. The D800s were subject to a maximum speed of 80 mph until all class members could be modified - this was not achieved until 1963. The "Bristolian" was decelerated by 5 minutes but an extra stop at Chippenham was inserted so that the drivers practically had no choice but to exceed 80 mph in order to keep to time. All speed running ceased after autumn 1960, when BR's timetabling methodology as a whole changed towards making all inter-city services more regular interval with standardised train formations and more intermediate stops. No longer would crack expresses such as the "Bristolian" be given such priority: the hope (largely successful) was to increase locomotive and coaching stock productivity and also increase passenger numbers in an attempt to curb BR's still-increasing monetary losses.

By 1964, the influx of both more powerful "Western" diesel-hydraulics and Class 47s drafted into the WR by BR's higher management, meant that some D800s were spared for use on the Waterloo-Exeter route. At this time, the Western Region (formed upon Nationalisation in 1948 largely from the Great Western Railway) had just assumed control of this line west of Salisbury from the Southern Region of British Railways and conveniently used the "no more crack expresses" edict to get revenge on its pre-Nationalisation rival the Southern Railway by withdrawing altogether the SR's "Atlantic Coast Express", which worked beyond Exeter, and replacing it with a semi-fast Waterloo-Exeter service hauled by D800s. The WR also took the opportunity to reduce its former rival's main line to single track for long stretches west of Salisbury and to sell off the "surplus" land - a move that is widely regretted today.

The late 1960s saw a brief revival in the fortunes of the D800s. By this stage they had been moved to duties such as Paddington-Birmingham (drastically reduced in importance since the 1966 opening of the electrified London Euston-Birmingham route, and re-routed to Birmingham New Street following the closure of Birmingham Snow Hill), and Paddington-Hereford. Rising traffic levels on the Paddington-Plymouth axis meant the WR aspired to an hourly service interval for this route with standard 10 and 12 coach passenger rakes. The maximum schedule was to be 4 hours 15 minutes for the 225.5 miles, but the "Cornish Riviera Express" would be retimed for 3 hours 45 minutes with stops at Taunton and Exeter only. The Westerns could only cope with these timings on 7 coach sets. The answer was to assemble pairs of D800s and reinstate the multiple working equipment on them, to allow the pair to be controlled by one driver. This was done with D819/22/23/24/27/28/29/31/32 and D866-69 and the acceleration in schedules did bring a further 7% increase in traffic levels. It was not, however, without its problems: a fault on one locomotive in a multiple-unit pair effectively disabled both and one alone could not keep to the schedules. By 1969 only two services were booked for a pair of D800s, albeit losing a further 15 minutes off the schedule, and the timetable was largely recast into separate Torbay and Plymouth trains, instead of being split en-route. This allowed the formations to revert to 8 or 9 coaches that a single Western could handle alone.


Preserved D832 Onslaught at Keighley on the Keighley and Worth Valley Railway, 19 June 2004.

Prejudice against hydraulic transmission in the higher echelons of BR's engineering divisions decreed in 1967 that all the WR's diesel-hydraulics were non-standard and should be withdrawn as soon as possible. Added to this were practical problems modernising the D800s: because of the scaled-down bodyshell there was very little room inside for extra equipment. It was, for example, physically impossible to accommodate a compressor as well as an exhauster, so the locomotives were unable to haul newer designs of air-braked coaching stock. It also proved impractical to equip them with electric train heating equipment, for similar reasons, so they retained unreliable steam heat boilers to the end of their lives.

The pilot build trio were all withdrawn by early October 1968 and by the end of 1972 all the others had been withdrawn. Many withdrawn examples were hastily cannibalised for spare parts to keep the others going as stocks had been reduced in anticipation of a swifter end to D800 operation than was in the event possible. The "Cornish Riviera Express" remained booked for two D800s until the end of 1970 but became notorious for late running because only one locomotive could be rostered; its partner would be failed for lack of a spare part. The early withdrawal dates meant that TOPS numbers were never worn, although the Swindon-built locomotives were allocated TOPS Class 42 and the NBL examples Class 43. Around 1971 an approach was made to BR seeking to purchase Class 22 D6319. A price was agreed but before the new owners could retrieve their purchase, it was scrapped at Swindon Works. An embarrassed BR offered the would-be owners their choice of the remaining Warships (D810/D812/D821 and D832) for the same price. D821 was chosen as it was in the best mechanical condition and thus became the first preserved ex-BR mainline diesel locomotive. D818 became a gate guardian on display outside Swindon Works but was scrapped in 1985. D832 was sent to the Railway Technical Centre at Derby where it was used for various research purposes until it too was secured for preservation. The others were scrapped. D832 was restored to full operational order using many of the parts from D818 and it is doubtful if there would have been enough components available to restore both D818 (which was missing several major items) and D832 without an expensive search for compatible German items. As of late 2006 only D832 is operational but the restoration on D821 is progressing towards running again during 2007.

Class details

The NBL-built locomotives are included for the sake of completeness.

Running number


Date to traffic

Date withdrawn



Sir Brian Robertson

11 August 1958

5 October 1968

Built at Swindon, lot no. 428. Date of order January 1956.



7 November 1958

3 August 1968



16 December 1958

5 October 1968



16 March 1959

1 January 1972

Built at Swindon, lot no. 437. Date of order February 1957.



23 April 1959

3 October 1971



13 May 1959

24 October 1972



3 June 1959

2 November 1972



24 June 1959

26 September 1972



8 July 1959

3 October 1971



19 August 1959

3 October 1971



16 September 1959

3 December 1972



14 October 1959

1 January 1972


The Royal Naval Reserve 1859-1959

12 November 1959

3 November 1972

Was to have been named Despatch



9 December 1959

1 January 1972



1 January 1960

7 November 1972



20 January 1960

3 October 1971

Name plates now on a narrowboat



17 February 1960

1 January 1972



9 March 1960

3 October 1971



30 March 1960

1 November 1972

Not scrapped until 1985



25 April 1960

3 October 1971



4 May 1960

2 November 1972



25 May 1960

3 December 1972




15 June 1960

3 October 1971



6 July 1960

3 October 1971



27 July 1960

3 December 1972



24 August 1960

23 August 1972



7 September 1960

18 October 1971



4 October 1960

1 January 1972



19 October 1960

28 May 1971



23 November 1960

26 August 1972



19 January 1961

26 March 1969



11 January 1961

3 October 1971



8 February 1961

16 December 1972




6 July 1960

3 October 1971

Built by NBL, date of order 3 July 1958, maker's order no. L100, Swindon lot no. 443



26 July 1960

3 October 1971



5 August 1960

3 October 1971



13 September 1960

22 May 1971



8 November 1960

22 May 1971



3 October 1960

27 March 1971



12 November 1960

3 October 1971



3 February 1961

26 April 1969



14 December 1960

3 October 1971


Royal Oak

20 December 1960

3 October 1971



2 January 1961

22 May 1971



16 March 1961

3 October 1971



7 April 1961

3 October 1971



12 April 1961

22 May 1971



22 April 1961

27 March 1971



27 April 1961

26 March 1969



29 May 1961

22 May 1971



8 June 1961

22 May 1971



10 July 1961

22 May 1971



24 July 1961

3 October 1971



30 August 1961

3 October 1971



26 September 1961

3 October 1971



25 October 1961

3 October 1971



16 November 1961

22 May 1971



11 December 1961

3 October 1971

Last NBL-built D800 to be withdrawn; Undaunted was simply switched off in full working order.



15 December 1961

3 October 1971



9 January 1962

27 March 1971



22 January 1962

27 March 1971



14 February 1962

3 October 1971



13 March 1962

3 October 1971



7 April 1962

26 March 1969



10 May 1962

27 March 1971

Was to have been named Zealous



28 June 1962

22 May 1971

Was to have been named Zenith



24 March 1961

1 January 1972

Built at Swindon, lot no. 448. Date of order April 1959.



26 April 1961

18 October 1971



18 May 1961

3 October 1971



12 July 1961

3 October 1971



25 October 1961

28 August 1971

Withdrawn following minor accident damage which was not deemed worth repairing.

Notes on withdrawal dates

The dates presented are as given by Reed. A correspondent in issue 137 of Traction magazine reports some inaccuracies in these dates. For example, the correspondent claims to have seen 828 Magnificent throughout June 1971 and on 4th July 1971 to have seen it hauled dead by NBL type 2 no. 6326 with fire damage and presumed to be heading for withdrawal at Newton Abbot depot. 831 Monarch worked the 16:05 Exeter St David's to Barnstaple service and 17:55 return on 6th October 1971, three days after its supposed withdrawal. 826 Jupiter hauled 808, D819, D822 and 868 on a Newton Abbot to Bristol service on 10th October 1971, being requisitioned at Exeter on its return run to haul the 16:05 Barnstaple service owing to a severe locomotive shortage. 812 is claimed to have been in use long after 3rd November 1971 and although 810 Cockade was withdrawn on 4th November 1971 it was reinstated on the 7th. On that same day, the correspondent notes 814 in use to power a convoy of 832 and 812 to Plymouth Laira depot where 814 was finally withdrawn, with 812 remaining in traffic. The situation with 832 is unclear because of its transfer to the technical department at Derby. The final four Warships of either kind (Class 42 or 43) in BR traffic were thus 810, 812, 821 and 824. 812 was in use on express passenger duties as late as 28th November 1972, over a year since its purported withdrawal. The last four locomotives were officially removed from capital stock on 3rd December 1972; 821 Greyhound hauled an afternoon Bristol to Plymouth parcels train on that day, being almost certainly the last BR Warship-hauled revenue-earning train.


Wikimedia Commons
has media related to:
British Rail Class 42
  • Reed, Brian. Diesel-Hydraulic Locomotives of the Western Region, David and Charles 1974. ISBN 0-7153-6769-2
  • Freeman-Allen, Geoffrey (April and May 1983). "The Warship Story". Rail Enthusiast p. 6 and 23

In fiction

Diesel 10 from the film Thomas and the Magic Railroad is based on the Class 42. There are some differences - most notably, Diesel 10, unlike the Class 42s, has a grabber named Pinchy on his roof.

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