Based on Worsdell's class S, Raven developed the class S2, which was intended for mixed service. The first seven locomotives were delivered without a superheater and the remaining 13 with a Robinson-type superheater. The first seven were also retrofitted later, but some also with Schmidt superheaters. The tender had a water scoop device to extend the range. The last built No. 825 was the first locomotive in the British Isles to use uniflow cylinders.

The locomotives were used to pull an express train in one direction and a freight train on the way back. Of the two-axle freight cars that were common at the time, each with a payload of ten tons, up to 80 could be pulled on flat lines and around 50 on hilly lines. The express trains often reached a weight of 350 tons.

The S2 was apparently unpopular with the crews because the boiler did not achieve sufficient evaporation performance if they were not familiar with the machine's peculiarities. The LNER took over all class S2 locomotives as class B15. Their decommissioning took place between 1937 and 1947.