Based on the 4-6-2 Karoo class locomotives, the Cape Government Railways ordered four “Enlarged Karoo” locomotives also designed by H.M. Beatty shortly before the founding of the South African Railways. In comparison to the original Karoo, they had a higher pitched boiler, larger wheels and larger cylinders. In contrast to earlier CGR locomotives, they had a Belpaire firebox and no round-topped one. They were only delivered in 1912 directly to the SAR and called class 5, while the original Karoo locomotives were called class 5A and 5B.

In 1935, in a time when many SAR locomotives got superheated A.G. Watson standard boilers, only one Enlarged Karoo got this boiler. In this process it was renamed class 5R it also got larger drivers, larger cylinders and a lower boiler pressure. While the unrebuilt locomotives were relegated to secondary services in 1928 and withdrawn in 1942, the single class 5R locomotive survived until 1969. For a long time it had been in use in suburban services around Cape Town and was regularly operated at 60 mph (97 km/h) until the mid-sixties.