BR Class 55 “Deltic”

The distinctive growl of the Class 55 “Deltic” cannot be mistaken. This locomotive remains a favourite for enthusiasts and crews alike. For many years, the Class 55 was the mainstay of the British Rail fleet on the East Coast Mainline, whilst whisking passengers to their destination faster than any locomotive previously. The “Deltic” was introduced during a time when British Rail was looking to standardise their diesel locomotives, of which, many example have not been successful, as they had various reliability issues, and accrued high maintenance costs due to the non-standard locomotive classes. However, the Deltic locomotives set the stage for high speed running in the future.

Steve Jones photo


Built by English Electric between 1961-1962, the Class 55 “Deltic” was the saving grace for the East Coast Main Line, and was at one point, the most powerful locomotive in the world. In the late fifties during the height of modernisation, British Rail capital was scarce and the agency sought to replace the remaining steam power on the ECML, and supplement the diesels currently serving on the line.

In 1947, LNER began peering into the age of diesel power, looking to replace the steam traction on the ECML, however, due to nationalisation on the horizon, this was decided not feasible. However, due to the various experiments with diesel power in the fifties, in was inevitable that diesel power was the future of traction, as it was cleaner and easier to maintain than steam.

In the early years of modernisation, the officials at BR believed that electrification was the future of railway traction. However, due to cost constraints this was temporarily abandoned, and thus, BR looked for alternatives to replace the aging steam power, such as the Gresley A4 Pacifics. During this time, English Electric subsidiary Napier had been placing their Deltic engines into maritime vessels, and were increasingly powerful. However, it was not until Lord Nelson of Stafford, who worked for English Electric at the time, experimented with the engines in locomotives, which led English Electric to place the Deltic engines in their DP1 prototype locomotive. British Rail executives took immediate interest and the locomotive, painted in a beautiful light blue paint, began testing on the London Midland region. Interestingly enough, a North American headlight housing was incorporated into the nose, as at the time, English Electric planned to build these locomotives for export as well, however, this plan never came to fruition.

Duncan Cotterill/railography

However, the Deltics were complex locomotives, thus, English Electric asked BR to not place them on passenger trains due to the possibility of breakdowns, and the inefficiency of the steam heater. Believably, because they did not want the locomotive’s reputation to be tarnished in the event of one of these failures. However, the locomotives had seamless performance when testing on freight duties and were soon assigned to the Merseyside Express from Liverpool to London, and the Settle and Carlisle route, both of which proved successful.

Although this powerful locomotive was proven in many areas of the system, its most successful runs were on the eastern region’s ECML, where it impressed eastern region General Manager Gerard Fiennes. However, due to height restrictions on the prototype, it could only operate between London and Doncaster. During its trials, the locomotive’s top speed of 100 mph paved the way for future high speed rail travel. Many crew members recall feeling the brute strength of the locomotive when at full throttle, feeling the forward surge of power in the cab. The cabs were noisy, however, and eventually underwent noise reduction treatments. In 1960, the production Deltic experienced a substantial oil leak and was withdrawn from service and donated the National Science Museum. In 1961, the first production Deltics were delivered and entered service on the eastern region, eventually, the twenty-two Deltics replaced fifty-five steam locomotives. Deltics that were based in the northern part of the eastern region were named after distinctive army cavalries, whereas the London based Deltics, in true LNER practice, named their locomotives after distinguished race horses.

Duncan Cotterill/railography

The Deltics served on the Eastern region for twenty years, achieving record miles and travel times during its time on the mainline. However, in the late seventies, upon the introduction of the High Speed Train (HST), the Deltics were slowly sidelined, as the they were unlikely to be transplanted to other regions, due to the train crew’s in other regions lack of knowledge of the complicated machine. Like many early BR diesels, the agency was seeking a standardisation of classes of locomotives, of which, the Deltics were not considered the standard type 5. In their later years, with parts at a scarcity, it was not uncommon to see the locomotives operating with only one Deltic prime mover.


The Class 55 Deltic sports two Napier Deltic D18-25 prime movers, capable of producing up to 1,650 hp each. The Deltic diesel engine was unique, as it was not developed for rail travel, however, it was developed for British navy vessels during wartime. The Deltic diesel was unlike any other, as it operated at a higher RPM than traditional diesels of the time. It idled at 700RPM, and when under full power, could reach up to 1500 RPM. Because of its 2 stroke design the Deltic was under increased pressure compared to other locomotives in the BR fleet.

The Class 55 was operated differently from other locomotives in the BR fleet, as it was maintained by replacing, rather than repairing.  When BR placed its initial order of 22 Deltic locomotives, it ordered 13 spare prime movers to be kept at Doncaster as a replacement. When a Deltic failed, it was brought into the shop, the failed engine removed and the spare installed. The failed engine was than repaired. This allowed the locomotives to have a higher availability, as they did not have to remain in the shop until the engine was repaired. This system of engine replacement took about a day, as opposed to a few weeks for other machines on the system, as other locomotives had to wait until the failed engine was repaired.

Duncan Cotterill/railography

A common theme among Deltics was its potent exhaust fumes. The locomotives had an exhaust collector drum which would accumulate oil, and when heated, would create blue plumes of smoke. This usually occurs at idle, and dissipates once locomotives are on their way. Despite this, the Deltics were seemingly reliable much in part to the efficiency of their maintenance regime.


After retirement the Deltics disappeared due to British Rail’s policy of not allowing non standard locomotives to operate on the mainline. It was not until privatisation that the Deltics again appeared on the mainline, due to private owners being able to run their trains on the mainline for a fee to Railtrack (now Network Rail). This began many excursions of the type and allowed younger generations of enthusiasts to experience the power and poise that the Deltic had to offer. In fact, 55022 “Royal Scots Grey” even worked freight and maintenance trains for a time with GBRf and Scotrail.

There were six Class 55’s preserved, along with two cabs purchased by private owners. The most notable preservationists of the Deltics is the “Deltic Preservation Society”, which owns three Deltic locomotives, including D9008 “ALYCIDON”, D9015 “TULYAR”, and 55019 “Royal Highland Fusilier”. The society is also in possession of the cab of 55008 “The Green Howards”.

D9000 “Royal Scots Grey” at Saltley on 22/08/99
Steve Jones photo

Additional entities have purchased preserved Deltics, such as 55002 “The King’s Own Yorkshire Light Infantry”, which currently resides in York. “Royal Scots Grey” 55022 is mainline certified, additionally, D9016, “Gordon Highlander” is also preserved. These locomotives are under the ownership of Locomotive Diesels Ltd, based in Crewe. Additionally, the prototype “Deltic” is preserved at The National Railway Museum in York. Five of these Deltics are operational, and can be seen operating on various excursion services throughout the country, and on heritage railways.


Although the Deltic was removed from service relatively early in its life, it paved the way for the future of high speed rail travel in Britain. The Deltic, although a complex machine, served the nation well with fast and efficient service. It is believed that the locomotive could have traveled from London to Edinburgh even faster if it the infrastructure had allowed. The Deltic came to the rescue of Britain’s railways during their time of need, and performed to the highest standard possible. The Deltic is remembered for its brute strength, style, and speed, as well as the contribution it made towards the nation.

Deltic Names

D9000/55022Royal Scots Grey
D9001/55001St. Paddy
D9002/55002The King’s Own Yorkshire Light Infantry
D9004/55004Queen’s Own Highlander
D9005/55005The Prince of Wales’s Own Regiment of Yorkshire
D9006/55006The Fife and Forfar Yeomanry
D9008/55008The Green Howards
D9010/55010The King’s Own Scottish Borderer
D9011/55011The Royal Northumberland Fusiliers
D9013/55013The Black Watch
D9014/55014The Duke of Wellington’s Regiment
D9016/55016Gordon Highlander
D9017/55017The Durham Light Infantry
D9019/55019Royal Highland Fusilier
D9021/55021Argyll and Sutherland Highlander


Number Built22
Wheel ConfigurationCo’Co’
Wheel Diameter3 ft 9 in
Wheelbase58ft 6in
Length69ft 6in
Width8ft 9 1/2in
Height12ft 10in
Weight99 long tons
Fuel Capacity900 imp gal
Prime MoverNapier Deltic D18-25 x2
GeneratorEnglish Electric DC Generator
Train BrakesVacuum

Later fitted with air

Max Speed100 mph
Horsepower1,650 hp x2
Tractive EffortMax: 50,000


Route Availability5


For further information on the history of British diesels, Greg Morse’s book “British Diesel Locomotives of the 1950’s and 60’s” takes an in depth look at the history of early dieselisation. (Link to Amazon)
Syd Young


Lifelong Rail Enthusiast and Owner of Worldwide Rails

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