Sir Nigel Gresley’s Legendary Locomotives


Considered one of the greatest locomotive designers of all time, Sir Nigel Gresley developed some of the most famous locomotives the world has ever seen. Gresley is responsible for engineering the world famous “Flying Scotsman”, an A3 Pacific type locomotive, and the fastest steam locomotive in the world, the A4 “Mallard”. Interestingly, one of Gresley’s hobbies was breeding different types of birds at his home, particularly waterfowl, which served as the inspiration for naming his locomotives, such as “Mallard” and “Bittern”.

Sir Nigel Gresley

Born in 1876 in Edinburgh, Scotland, Gresley would soon matriculate to Derbyshire, where he spent much of his childhood. As a young man, Gresley left college to work on the railway. Gresley began his career on the railway, beginning an apprenticeship at the London & Northwestern Railway at Crewe Works, and later at the Lancashire and Yorkshire Railway(L&YR). While at the L&YR, Gresley quickly moved up the ranks. By 1902, young Gresley was named Assistant Works Manager at Newton Heath Depot, and in 1903, became the works manager, and later, the Assistant Superintendent of the Carriage and Wagon Department.

In 1905, Gresley left the L&YR, and began a new chapter at the Great Western Railway (GWR). This is where he was introduced to Doncaster Works, where he would engineer the most famous locomotives ever built. Upon arriving at GWR, he was given the position of Carriage and Wagon Superintendent, and six years later, became the Chief Mechanical Engineer (CME). During his tenure at the GNR, he began his legacy by introducing the 4-4-2 “Atlantic” type locomotive to Great Britain, as there was a need for heavier and faster trains with greater capacity.

Gresley soon began engineering new coaches for the non-stop London-Edinburgh route, the “Flying Scotsman”, which included heavier coaches fitted with buffet cars. Because of the heavier carriages, two locomotives would have to be used, which would be an astronomical cost to the railway, as they would need two sets of crews, and double the maintenance costs of locomotives. It was decided that in order to avoid the high costs of having to double head locomotives, new, heavier locomotives would need to be constructed. This resulted in the engineering of the A1 locomotives.

During the early twenties, the government began to consolidate many railway companies, creating the “Big 4”, this was enacted by the Railways Act of 1921. During this time, Gresley was engineering his A1 class locomotives for the GNR, which would soon be transferred to the LNER in 1923.

A few years after the Railways Act of 1921 was put into law, the nation’s railways consolidated in 1923, one of which new companies being the London & Northeastern Railway (LNER), where Gresley would soon find a home. The LNER was formed from seven smaller railways, including the Great Northern Railway and began operations in 1923, while Gresley maintained his position as Chief Mechanical Engineer at Doncaster.

Hugh Llewelyn photo

Built at Doncaster Works, which was coined “The Plant”, the newly built Gresley A1 locomotives were readied for service, and were the LNER’s premier express locomotives which were capable of hauling a 600 ton train at 50 mph. Gresley continued to engineer improvements to the A1 locomotives, including chimney improvements, deflector plates, upgraded tender, and other improvements. Due to the alterations of the locomotive, they were reclassified as A3 class locomotives. A total of 52 A1 locomotives were rebuilt into A3s, with 27 A3s built new from Doncaster.

Perhaps the most successful locomotive that Gresley designed was the streamlined A4 Pacific. This engineering marvel was completely streamlined and broke many records throughout its life, especially speed records. Gresley’s  A4 “Mallard” holds the speed record for steam traction, traveling at 126 mph in 1938, a record that has not yet been broken by steam traction.

Gresley was perhaps so successful, because not only was he an experienced mechanical engineer, but he was constantly in the public eye. He relayed his many successes with the media and held various publicity events to promote his designs, especially when his creations conducted their record breaking runs.

Gresley passed in 1941, after a bout with an illness, and was buried at his church in Derbyshire. However, his legacy lived on, as his designs and innovations shaped the future of railways in Great Britain and the world. A statue of Gresley was placed in London Kings Cross station as a monument to the many engineering feats accomplished throughout his life.

Contributions to Locomotive Design

Gresley is remembered for changing transport in Great Britain, and furthermore, creating innovations that were used throughout the world. Gresley’s locomotives were so successful because of his many innovations that improved aerodynamics, running gear, and reliability.

These inventions included the introduction of the Gresley conjugated valve gear, which allowed the ability for locomotives to have three cylinders with only to sets of valve gear for the outside cylinders, which was made possible by a series of levers, where the third lever can imitate the first two, operating the middle valve gear. This increased speed, while reducing maintenance costs.

Gresley, who had a knack for improving efficiency, sought to develop a solution to prevent trains having to stop for crew members. Gresley engineered the corridor tender, which featured a passageway on the right,and a gangway connection on the rear. This allowed crews to switch halfway through the eight hour run from London Kings Cross to Edinburgh Waverly.

Additionally, Gresley developed the articulated railway carriage, which increased passenger comforts by increasing ride quality. This type of carriage continued to be used on many high-speed services in the years following Gresley’s innovation, in the form of the electric multiple unit (EMU).


Gresley’s locomotives inspired innovation and advancement in the railway industry. Many railways throughout Britain adopted the streamlined concept that Gresley had introduced, which improved speed and efficiency. Gresley’s work was soon renowned in the railway industry, and beyond.

Gresley A1 4-6-2 Pacific

The first Pacific type locomotive to grace Britain’s railway, the A1 class locomotive was built to accommodate the need for a larger locomotive to haul heavier passenger carriages. The A1 was engineered by Gresley, becoming one of his most successful locomotive models. By 1915, the Pennsylvania’s Railroad’s new K4 Pacific was a successful locomotive model that had proved its reliability. Gresley designed his locomotive similar to the K4 design, however, made his own modifications.

These locomotives were engineered during final years of the Great Northern Railway, and were delivered a year before the LNER was formed. This locomotive’s 4-6-2 wheel arrangement allowed it to haul heavy carriages at speed, and became the mainstay passenger express locomotive of the LNER.

Public Domain

Gresley designed these locomotives for speed, efficiency, and power. With this in mind, he engineered the locomotive with a large boiler, rated at 180 pounds per square inch and a large rounded firebox, much like its GNR ancestors. This construction caused the locomotive to be built to the maximum specifications of the loading gauge for the LNER. A unique Gresley design was the addition of his precision engineered  valve gear. This valve gear made it possible to set the locomotive up for 3 cylinder operation.

In total, there were fifty-two A1 locomotives built, and were slated to overtake the position as the premier passenger locomotive for the then GNR, which was previously the large boilered Atlantics, which were beginning to reach their operating capacity for the route. There is one A1 locomotive that was preserved, No.4472 “The Flying Scotsman”, which is currently in operating condition.

Gresley A3 4-6-2 “Super Pacific”

The A3 locomotive is the result of various tests performed on the A1 to improve efficiency and shorten journey time. The A1 locomotive, although reliable and quick, had its downfalls.

The A3 upgrades included a larger boiler, cylinders, increase of superheating mechanisms, improved weight distribution, and long-travel valves. Crew improvements were implemented, such as the driver’s seat switching from right to left in order for increased visibility of signals. Service speed was improved with the addition of the “corridor tender”, which provided a five foot walkway through the tender to the locomotive, which was lit by a window in the back of the tender. This allowed the crew to switch on the fly, instead of conducting a stop, therefore, decreasing travel times. The corridor tender could handle 5,000 gallons of water, and nine long tons of coal. These modifications allowed increased customer comforts and speed, by decreasing the travel time between London and Edinburgh.

Corridor Tender on “Flying Scotsman”
Public Domain

All of the existing A1 locomotives were upgraded to A3 standards, as well as construction of twenty-seven new A3s, produced at Doncaster Works. Gresley continued to experiment with the new A3 locomotives, aiming to control the exhaust of the locomotives that was affecting the view of the driver. A number of test were administered, including placing miniature smoke deflectors on the sides of the chimney as well as replacing the chimney with a double stove pipe style. During the beginning of British Rail, smoke deflectors were added on either side of the locomotive.

Gresley A4 4-6-2 Streamlined Pacific

Perhaps Gresley’s finest creation, the A4, with its streamlined casing, brought about a new era of speed and efficiency for the LNER. Thirty-five examples of the type were constructed at Doncaster Works between 1935-1938.

The A4 class of locomotives was introduced to haul the streamlined “Silver Jubilee” between London King’s Cross and Newcastle. Beginning in 1935, four A4s were completed, and began breaking speed records during testing. The “Silver Link”, broke the speed record for steam traction, traveling 112.5 mph, and averaged 100 mph over the course of the run. Gresley soon appreciated the benefits of streamlined trains, and due to the success of the “Silver Jubilee” two more streamlined trains called “The Coronation” and the “West Riding Limited” were introduced, requiring the production of additional A4 locomotives.

Hugh Llewelyn photo

Gresley engineered these locomotives for express passenger service, citing its higher boiler pressure, larger firebox, and decreased usage of coal and water. The aerodynamics continued to improve by implementing the Kylchap double chimney.

The A4 locomotives are known for smashing almost every record in the book. The most notable being the record breaking run of the “Mallard”, when it reached a top speed of 126 mph, the fastest of any traction during this time. During its run, it had 6 coaches and a dynameter car, which was used to measure the performance of the locomotive, which amassed to 240 tons. Today, the Mallard is on static display at the National Railway Museum, along with the film from the dynameter car, showing the evidence of the record breaking run.

Gresley P1 2-8-2 Mikado

The Gresley P1 locomotive is one of the rarer locomotives on the LNER roster, with only two example of the type being constructed at Doncaster Works in 1925. This 2-8-2 Mikado type locomotive was built for freight service between London and Peterborough, however, were not fit for this service, and was relegated to the route between New England shed and Ferme Park. At the time of production, this locomotive was considered the largest and heaviest locomotive in Britain.

Quickly proving themselves as able freight haulers, these locomotives were known for their brute strength and reliability. However, efficiency was not their strong suit, as the locomotive consumed 131 pounds of coal per mile of travel. However, LNER officials developed a liking for the locomotive so much so, that addition examples were considered, however, this plan never came to fruition.

Public Domain

Adding to the uniqueness of these locomotives, boosters were allocated on the rear truck. These boosters were activated by a pump located on the boiler, which engaged the cylinder clutch. Gresley engineered these booster motors to assist locomotives when battling a grade or incline. However, the boosters were not useful, as they were troublesome for the crew and caused numerous mechanical problems, and were later removed.

The P1 locomotives were genuinely producing more power than needed for many trains, therefore, were deemed uneconomical. They underwent an overhaul in 1942, receiving new boilers and reduced the cylinder diameter to 19 inches. After rebuild, the locomotives were referred to as Class P1/2. Both locomotives were withdrawn in 1945 and scrapped.

 Gresley Class U1 2-8-0+ 0-8-2

The U1 locomotive was the largest locomotive to traverse Britain’s rails. It was a Beyer-Garratt type locomotive, of which, the locomotive is articulated into three parts, which includes the boiler on one frame, and two steam engines on two separate frames. In the case of the U1, it was considered to be two GNR 2-8-0 “Consolidation” type locomotives.

This locomotive was built including its articulated design to tackle the tight curvature of the Woodhead route, as it was meant to be used as a banking locomotive, which acts as a helper engine on the rear of a train. The locomotive was produced by Beyer, Peacock of Manchester, with an original order for two, however, decided on just a single locomotive. The locomotive joined the LNER in 1925, and was promptly assigned to banking trains over the steep Woodhead route.

Public Domain

The trains that the U1 helped to bank were well over sixty wagons long, with usually an LNER O4 leading, with another O4 trailing, and the U1 being attached to the train at Wentworth Junction. Although the power of the U1 was effective, it was not popular with train crews, as it was considered to be twice as much work to operate than a traditional locomotive. Perhaps the worst experience for the crew was negotiating through the Silkstone Tunnels, which was already filled with smoke from the other locomotives on the train. This made for uncomfortable conditions for the crew with the likes of heat and steam, which resulted in the railway installing gas masks in the locomotive for the use of the crew.

Because the Woodhead route was electrified in the mid-fifties, the U1 needed to find alternative work, and was tested on the Lickey Incline to assist 0-10-0 banker locomotive coined “Big Bertha”. However, due to visibility issues, the U1 was instead placed into storage until 1951, when the locomotive was yet again banking trains. It was again withdrawn in 1952, when it was sent to Gorton Locomotive Works, where they tried to convert the locomotive to burn oil instead of coal, and an electric headlight was added before being returned to the Lickey Incline in 1955, however, was withdrawn and scrapped a few months later.

Gresley K4 2-6-0 “Mogul”

Designed for the West Highland Line in Scotland, the K4 was useful as there was no longer a need to double head locomotives on the West Highland Line, and were very popular with train crews. The locomotive performed best on inclined stretches of track, as the locomotive shook and rattled at speed on flat land.

After the incorporation of British Rail, these locomotives could be seen almost anywhere around Scotland, before being officially withdrawn from service in 1961. Today, a single K4 is preserved called “The Great Marquess”, and is today owned by Scottish farmer John Cameron. The locomotive could be seen hauling railtour trains until the steam ban in 1968. During this time, it was stored at the Severn Valley Railroad until it was overhauled at Crewe in 2004-2005. The locomotive emerged from overhaul and toured around the UK, visiting places it had not gone to during its life with LNER and British Rail. The locomotive is now stored, and considered permanently retired, and will be displayed in a museum Cameron is having constructed on his farm.

Related information regarding Sir Nigel Gresley

Flying Scotsman

The Gresley Society Trust



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