In 1904, the CSAR received 15 class 10 Pacifics from North British for express service. An innovation for South Africa, they had a wide firebox that was located behind the last driving axle and above the trailing axle. Due to its suitability for poorer coal and the possible greater power, this design quickly became established. Together with the class 11 Mikados, they were at the time the heaviest locomotives ever built for the Cape Gauge. This was only possible because the CSAR had laid heavier rails weighing 80 instead of 40 pounds per yard.
In 1910 another class 10 locomotive was placed into service, now supplied by ALCO. It was used to compare the locomotives otherwise sourced from Great Britain with American ones. This locomotive had a bar frame instead of the plate frame common to British manufacturers and was delivered directly with a superheater.
class 10D by Baldwin
The 15 British machines were also retrofitted with a superheater in 1910. They were still called class 10 when renumbered by the SAR in 1912, while ALCO's single one formed class 10D. The latter was scrapped in 1931. The others were used on commuter and suburban trains from 1959 after some key main lines were electrified. They were retired by 1972 and two were preserved.