In 1934, William Stanier had 37 2-6-4T tank locomotives built at Derby which were numbered 2500 to 2536. In most respects they were based on Fowler's 2-6-4T. But the new locomotives were intended for heavy suburban traffic with tight schedules over the old London, Tilbury and Southend Railway line. To get high acceleration rates despite large driving wheels with a diameter of 5 ft 9 in or 1,753 mm, they got three cylinders. Although they fulfilled their requirements, the third cylinder led to complicated maintenance.

To ease maintenance, production of a two-cylinder variant started in 1935. The diameter of the cylinders had been increased from 16 to 19 5/8 inches to get a similar tractive effort with the same boiler pressure. The boiler was somewhat larger in all dimensions. By 1943, nine batches had been produced at Derby and two by North British for a total of 206. Between the batches, there had differences in the surface of tubes, flues and the superheater. 

From 1945, Fairburn's 2-6-4T was built on the basis of Stanier's design with the same boiler. Withdrawals started in 1960. The last three-cylinder locomotive was gone in 1962, but the last one with two cylinders only disappeared in 1967. The only one that is still existing today is 2500, the first to be built. It belongs to the National Railway Museum at York, but was moved to the Bury Transport Museum in 2023.