The class HF was a 2-8-2+2-8-2 Modified Fairlie that did not only have two driving axles more than the preceding classes FC and FD, but also a higher axle loading. The class designation should have been “FE”, but obviously “HF” was chosen to denote it as a “Henschel Fairlie” in contrast to the other Fairlies built by North British. It had a direct competitor in the class GE Garratt with the same wheel arrangement that was introduced two years earlier.

When put into service, they had some problems with steam production which had to be addressed in the Durban Workshops. A general problem of Modified Fairlies were the overly long frames which did not only have to carry the boiler, but also the supplies. So there were often cracks in the frames and also the pivot bearings were subject to a huge amount of wear and tear. So all in all, they were not as successful as the Garratts and no further Modified Fairlies were ordered by the SAR. The eleven class HF locomotives were withdrawn by 1951.