In 1918, the South African Railways placed eight Class MJ1 Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in branch line service.

Hendrie, the Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922.

Eight of these branch line locomotives were built and delivered by MLW in November 1918, numbered in the range from 1666 to 1673.

[1][2][4] The locomotives were superheated, had Walschaerts valve gear and, like the Class MJ Mallets, had Belpaire fireboxes, but slightly larger boilers.

Day was the CME of the SAR, the Classes MJ and MJ1 were modified slightly to be reboilered with the same standard boiler.