The CLTB elected to build only the light type to allow it to operate on any narrow gauge line in Australia. After an attempt to obtain drawings and licenses from Beyer, Peacock and Company failed, in July 1942 the CLTB recommended to the War Cabinet that 30 locomotives be built locally. In August 1942, the War Cabinet approved the order, this was increased to 65 locomotives in November 1942. The Western Australian Government Railways' Chief Mechanical Engineer Frederick Mills was seconded to lead a team of engineers in Melbourne to design the new locomotive. The Queensland Railways were vocal opponents, stating its preference for a modified version of its C17 class.