 The class nevertheless contained several ‘modern’ features such as a Belpaire firebox, superheater, and a side-window cab.It was the last Southern steam locomotive design before the Second World War, and represented the final design of Maunsell's career, as he retired due to ill-health in 1937.Maunsell’'s successor, Oliver Bulleid, oversaw the building of twenty members of the class at Eastleigh railway works between January 1938 and September 1939.