For the Metropolitan and District Lines in London, Joseph Armstrong designed the Class 355, also known as “Metropolitan Tanks” or simply “Metro Tanks”. It was created with a driving wheel diameter of just five feet to ensure adequate acceleration. Since the underground tunnels were also to be run through, many locomotives were fitted with a condensation device. No driver's cab was installed, as Armstrong believed it would have reduced staff attention.

With enlarged water tanks and leading axle in outside frame

Locmotive Magazine, March 1903

The first 60 machines were built between 1868 and 1878 in three series of 20 units each. In the first two series, all axles were mounted in the inside frame, in the third series the leading axle was in external bearings and the wheelbase of the coupled axles was slightly larger. In the early years, the locomotives were also required to haul goods trains within London city limits until the Class 633 became available. After Armstrong's death, a total of seven more series with a total of 80 more locomotives were procured by William Dean between 1878 and 1899. These had a larger boiler and larger supplies.

No. 3593 rebuilt as 2-4-2T

Locmotive Magazine, December 1905

In the 1880s, the first series were already being rebuilt with a larger boiler and larger water tanks. Half and fully enclosed driver's cabs were retrofitted in later years. The first of the older machines were already retired around 1900. However, the newer ones in particular were used for a longer period of time.

With the electrification of the Metropolitan and District Lines in 1905 and 1907, the locomotives were also used on other lines. For this purpose, the condensation devices were removed and partially a push-pull train control was installed. For the routes of the underground, the GWR kept about 50 machines available until about 1930, which were then replaced by the class 6100 Large Prairies. Other locomotives were used in more rural regions and some were even used on the main line. In the thirties most were retired. A total of ten were still in existence when British Railways was founded in 1948, but these disappeared by 1949.

The GWR class 2021 was a 0-6-0 tank locomotive introduced in 1897. It was directly based on the class 850 of 1874, but had a longer wheelbase to fit a larger firebox. The design is generally being attributed to George Armstrong, but since he retired in 1897, the innovation to build the new class might also have come from this successor William Dean. Like the class 850, the class 2021 originally also had a saddle tank.

When Churchward wanted to fit a Belpaire firebox, due to its square profile, pannier tanks had to be fitted. Most of the class was rebuilt in this way, but this process took until 1948 to be completed. By this time, British Railways took over 110 locomotives. Starting in 1949, the first ones were replaced by the class 1600 that was still based on the same design of 1874 and had dimensions which were very similar to the class 2021. In 1959, the last was withdrawn.

As a successor to the fast suburban Class 3600 “Birdcage”, Churchward developed a tank locomotive from the Class 3800 “County” by adding a trailing axle and storing water and coal supplies on the locomotive. It used the slightly smaller GWR Standard No. 2 boiler, which also had a Belpaire firebox and was tapered towards the front. Only number 2230 received the same County class boiler, but was also quickly upgraded to the smaller standard boiler.

The side water tanks had a forward sloping ceiling to match the tapered boiler barrel. They allowed the water capacity to be increased from the 1,500 gallons of earlier tank locomotives to 2,000 gallons, retaining good forward visibility. Scooping devices for water troughs were installed in both directions of travel in order to be able to fill up the water supplies more quickly during operation. Thanks to the driver diameter of 80.5 inches, the magazine “Die Lokomotive” still assumed in 1932 that it had to be the fastest tank locomotive in the world.

Between 1905 and 1912, three series of ten engines each were manufactured. The locomotives of the third series had a superheater installed ex works, and this was retrofitted to the first two series. Likewise, some locomotives were later provided with larger supplies. They were used in front of fast passenger trains in the suburbs of London.

Schematic drawing with dimensions

Locomotive Magazine, August 1905

Thanks to the large wheels, the engines were suitable for use on the outer suburban lines without many intermediate stops. At the same time, however, this meant that the acceleration was not sufficient for the inner suburban routes. Another point of criticism was the insufficient running smoothness, since the wheelbase of the two coupled axles was very small and there were large moving masses due to the long cylinder stroke of 30 inches. So it came about that the “County Tanks” were replaced by the “Large Prairies” of the 6100 class between 1931 and 1934. With their driver diameter of 68 inches and three coupled axles, these represented a better compromise between speed and acceleration. Since no better area of application could be found for the class 2221, they were all scrapped.

A total of 260 class 2301 freight locomotives built for the GWR between 1883 and 1899 were also known as “Dean Goods” after their designer. They had a Belpaire firebox and, unlike previous GWR locomotives, only had an inside frame. Due to their high tractive power compared to four-coupled locomotives, they were also used for passenger and express trains. From 1908 they received new boilers and cylinders enlarged by half an inch. 20 of them were rebuilt into class 3901 tank locomotives with a 2-6-2T wheel arrangement. In both the First and Second World Wars, they were used by the ROD in France, among other places, and were then partly sent to other countries. British Railways took over 54 locomotives in 1948 and used them mainly on branch lines in Wales due to their low axle loads. The last machine was retired in May 1957.

For the coal traffic between Aberdare and Swindon, the GWR had 81 2-6-0 locomotives built from 1900 onwards, also called the “Aberdare class”. It was built under Dean and the first to be built, number 33, still had a conventional boiler with a Belpaire firebox, which the 4-4-0 express train locomotives of the Bulldog class also had. All others already got Churchward's tapered boiler. The last nine were rebuilds of the class 2602 “Kruger”.

A striking feature was the massive outside frame. The first ones received a superheater as early as 1908. The first withdrawals took place from 1934, but some were reactivated again during the Second World War. There were twelve remaining when British Railways was founded, but they disappeared by 1949.

In the search for a modern generation of express locomotives for the GWR, Churchward, who had been appointed chief engineer in 1902, undertook a number of trials. The result of this process was the Saint class, which formed the basis for the GWR's further two-cylinder 4-6-0s. These were the classes named Hall, Modified Hall, Grange, Manor and County, with the County class only appearing in 1945.

It started with three prototypes from 1902 and 1903, all of which had the 4-6-0 wheel arrangement and two cylinders, but differed in some details. They were also compared with a French De Glehn compound Atlantic, so one of them was also rebuilt into an Atlantic. A key factor turned out to be that the ports of the valves had to be significantly enlarged compared to the usual dimensions at the time in order to be able to supply sufficient steam for large cylinders. This led to the building of the first production machines in 1905.

These were mostly named after characters in Sir Walter Scott's novels and consisted of six Ten-Wheelers and 13 Atlantics. They had a tapered boiler with no superheater but with a high boiler pressure of 225 psi or 15.5 bars. Since Churchward appreciated the additional tractive power of the Ten-Wheelers, the Atlantics were also rebuilt into Ten-Wheelers.

In 1906 ten more locomotives were built, which were referred to as “Lady class” because of their names. Among them there were differences in the length of the firebox and the tubes in the boiler. No. 2901 “Lady Superior” was built with a modern Schmidt superheater, while the others received a Swindon No. 3 superheater between 1909 and 1911. The 2903 “Lady of Lyons” is said to have reached a speed of 120 mph or 193 km/h running light on a slight down gradient of 1 in 300 in 1906, but this must be doubted due to the inaccurate measurement methods.

No. 181 “Ivanhoe” in its original form als Atlantic

GWR

In 1907 the 20 locomotives of the actual Saint class were built. These were also soon retrofitted with superheaters. From 1911 onwards, 25 Court class locomotives followed, which were the first to have a superheater from the start and whose cylinders were half an inch larger. Here, too, there were small differences in the boilers between the individual locomotives.

After the Castle class took over the fastest express trains, the Saint was also used in front of express freight trains. Since the wheel diameter of 6 ft 8 1/2 in or 2,045 mm was not very suitable, Collett developed the Hall class with smaller wheels. The prototype was created by rebuilding the 2925 “Saint Martin” with six-foot wheels.

The Saint class is considered groundbreaking not only because of its successors at the GWR, it also generally set standards for further development. They were decommissioned between 1931 and 1953. Since no member of the Saint class remained, the Hall class's descent from it was remembered. So No. 4942 “Maindy Hall” was rebuilt into 2999 “Lady of Legend” between 1995 and 2019.

The Class 3031 of the Great Western Railway, also known as the “Dean Single”, was created from the conversion of 30 examples of the Class 3001, which had been built by William Dean in the 7 feet 1/4 inch broad gauge and were converted to standard gauge a short time later. Since an increase in power through a wider boiler was impossible with the standard gauge due to the limited space between the large wheels, the boiler was extended to the front. After the leading axle derailed in the middle of the box tunnel due to the increased weight, it was replaced with a bogie, resulting in the class 3031. Since the cylinders were located below the smoke box in class 3001, a special bogie had to be constructed. This could be pulled out after loosening four screws and slightly lifting the front part of the locomotive to ensure uncomplicated maintenance of the smoke box and cylinders.

No. 3050 “Royal Sovereign”

J.R. Howden, The Boys' Book of Locomotives

First, two class 3001 locomotives were converted in March 1894, the remaining 28 were converted between June and December of the same year. A total of 50 more were factory built between 1894 and 1899. In use, the class 3031, like other locomotives with a 4-2-2 wheel arrangement, excelled with high sustained speeds. On May 9, 1904, a mail train was able to travel the 117 miles from Bristol to London-Paddington in just under 100 minutes for the first time, which corresponds to an average speed of around 70 mph. However, since one driven axle was soon no longer sufficient, they were decommissioned between 1908 and 1915. Today there is a replica of No. 3041 “The Queen”, which was completed in 1982.

Based on the Prairie locomotives later known as the class 3100 and class 5100, the GWR had 41 units of a reinforced variant made as the Class 3150 in 1906. The standard type 2 boiler was replaced with a larger type 4 boiler, which was mounted slightly higher here. Due to the higher weight, the axle load was assigned to the “Red” category instead of “Blue”, which reduced the area of use of the locomotives compared to their predecessors. However, the main suburban routes were string enough to allow the use of these locomotives. So they pulled the heavy local trains on these routes. The machines were retired between 1957 and 1960.

As early as 1938, the then chief engineer Charles Benjamin Collett had started a rebuilding program of five engines, which were to be used for pushing on ramps. These reduced the coupling wheel diameter by five inches to 1,600 mm, increased the boiler pressure from 200 to 225 psi and increased the cylinder diameter by half an inch. This increased the tractive effort by more than 20 percent. These machines were known as the Collett class 3100, but the number remained as five.

For express trains on more hilly main routes, such as Devon and Cornwall, William Dean envisaged 4-4-0 locomotives with a coupled wheel diameter of five feet and eight inches. Based on his Duke class, he built No. 3312 “Bulldog” in 1898 with a larger boiler. Like the Duke, it had an outer frame that had recesses in the area of the cranks of the coupling rods. The boiler also had a steam dome, but the new boiler caught the eye with a raised Belpaire firebox. 

No. 3707 “Francis Mildmay”, later No. 3417 “Lord Mildmay of Flete”

The boiler was designed by George Jackson Churchward, who was still Dean's assistant at the time. The boiler was to become the GWR's standard boiler No. 2 and initially had a consistent diameter from back to front. In October 1899, No. 3352 “Camel” was completed, which is considered the first production example of the Bulldog class. With it, the boiler no longer had a steam dome and tapered from the back to the front.

No. 3733 “Chaffinch” from the Bird class

Locomotive Magazine, June 1909

In the following years several series were created, which showed some differences among themselves. Some continued to have a parallel boiler and others had a tapered boiler of varying design. Soon, the tapered boiler prevailed, as well as straight outer frames. Although the locomotives were initially referred to as the Camel class due to the first production engine, the prototype's name "Bulldog" soon caught on.

By 1909, 141 Bulldog-class examples had been built, 20 of which had been converted from existing Duke-class locomotives. In 1909 and 1910, another 15 examples of a slightly modified design, known as the Bird class, were built. It differed from the Bulldog class mainly in higher outer frames, a new bogie and a longer smoke box.

All locomotives of the two classes were retrofitted with a superheater between 1910 and 1914. Since the 4-4-0 locomotives of the GWR were initially provided with different number ranges across the classes, they were renumbered in 1912. The locomotives of the Bulldog and Bird classes received the number range between 3300 and 3455 without gaps. In August 1929, the first machine of the Bulldog class was decommissioned, but the decommissioning did not take place in larger numbers until 1934 and the last example survived until 1951. From of the Bird class, the first example only disappeared in 1948, but the last one also in 1951.