The benefits gained by Maunsell's modifications showed in the improved performance of the first batch of Maunsell S15s over their Urie-built predecessors. A third batch was ordered in 1931, coinciding with a downturn in the volume of freight due to the Great Depression. This meant that the last of the S15 class was not completed until 1936, although weight-saving modifications were undertaken to this batch. A final modification was also applied to the class at this time, when all locomotives were equipped with smoke deflectors to improve visibility from the footplate when travelling at speed.Russell (1991). p. 383. This modification was a feature that became common to most Maunsell-influenced designs.
