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.