Railway, and was one of a number of Midland features introduced by Maunsell's chief draughtsman James Clayton, who transferred to Ashford Works in 1914 from the Midland Railway. Variants of this cab became standard for all new Southern Railway locomotives and converted tank engines. Other modifications included the lengthening of valve travel, and fitting larger outside steam pipes to streamline the flow of steam into the cylinders. Fifteen locomotives of this revised design were built in 1927, and some were given six-wheeled tenders for use on the Southern Railway's Central section. This allowed the locomotive to be turned on the shorter turntables found on this part of the network. From new, the rest of the class was equipped with the Urie eight-wheel bogie tender, which allowed the class to operate on the extended freight routes of the Southern Railway's Western section. The standardisation measures undertaken by both Urie and Maunsell were soon vindicated by the fact that tenders and other parts were swapped with those of other classes on the Southern Railway when locomotives were under overhaul. Third batch – Maunsell 1936 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. This modification was a feature that became common to most Maunsell-influenced designs. Operational details After modification by Maunsell, the S15 class was regarded by locomotive crews as an excellent goods engine best known for working heavy night express goods trains between Exeter, Southampton and Nine Elms. The S15s were also very capable passenger engines, being able to deputise in situations where there was a shortage of passenger locomotives during peak holiday periods. Both Urie and Maunsell S15s spent most of their working lives on the Southern Railway's Western section, although they were sometimes used on inter-regional freights. In order to increase maintenance efficiency, all Urie S15 locomotives (which had the lower boiler pressure) were concentrated at the Southern Railway's London freight depot at