The unsatisfactory results of the unreliable and high-maintenance M-class Mallets led the Kenya-Uganda Railway to switch to Garratt-type locomotives. They weighed over 120 tons loaded, had a Belpaire firebox and were among the most powerful meter gauge locomotives of their time. The first four to be delivered came in 1926 from Beyer, Peacock & Co. and were designated class EC. They were fired with eucalyptus wood, which soon proved inefficient and dangerous for the crew. Thus, a conversion to coal firing took place, but they were already sold to Indochina in 1939.

20 of the class EC1 were purchased in 1927, which were essentially identical to the EC but were coal-fired from the start. Two more followed in 1930, which differed from the 1927 batch in minimal details. For this reason, the East African Railways made the first batch the class 50 and the second batch became class 51. Ten more oil-fired locomotives followed in 1931, which ran as EC2 on the KUR and later became class 52 on the EAR.

With the Garratts, the train loads could be significantly increased compared to the older locomotives. Up to 440 tons could now be hauled on the non-upgraded stretches with a gradient of up to two percent, on which the older eight-coupled vehicles could haul a maximum of 200 tons. They also hauled passenger trains at higher speeds on the upgraded line between Mombasa and Nairobi. They were mostly phased out in the 1950s and some of the bogies were reused to rebuild class 13 tank locomotives from a 4-8-2 to 4-8-4 wheel arrangement.