In order to expand the capacity for hauling heavy passenger trains in the western and central parts of the Cape Colony, H.M. Beatty developed the first Class 6 locomotives to the specifications of Superintendent Michael Stephens. With a driver diameter of 54 inches, they were quite suitable for faster trains for the proportions of cape-gauge locomotives of the 1890s. The 40 examples were supplied by Dübs in Glasgow and introduced a new three-axle tender carrying 5 and a half tons of coal and 2,846 gallons of water.

The locomotives fully met the expectations placed on them and proved to be extremely inexpensive to maintain. In 1897, ten units were sold to the Oranje Free State Railways and operated there as Class 6-L. When the Orange Free State fell to British troops after the Second Boer War, they came to the Central South African Railways as Class 6-L1s. Their manager even suggested using the locomotives to set up a 48-hour connection for the 870 mile route from Cape Town to Johannesburg.

With the formation of the South African Railways they continued to be listed simply as Class 6 because they were the first of their kind. As the Class 6 was gradually replaced by more powerful locomotives in the role of fast passenger trains, it developed a reputation as the „jack of all trades”. They were to be found in front of almost all types of trains for several decades, and seven were even delivered to Sudan during World War II. The last examples were not retired until 1973, when they had been in service for 79 and 80 years respectively. Three examples remain today, one of which is operational and used intermittently by Rovos Rail to power the Pride of Africa luxury train.