In 1899, Swindon built two mixed-traffic prototypes designed by William Dean. While number 2601 was a 4-6-0, number 2602 was a 2-6-0. Their rugged design was likely influenced by Churchward and and their main feature were the large outside plate frames which concealed part of the driving wheels which measured four feet and seven and a half inches. The cylinders had a small diameter of 19 inches and a long stroke of 28 inches to fit between the frames. Their boilers had a Belpaire firebox with a combustion chamber and were pressed to 180 psi. Above the front part of the boiler, there was a saddle-shaped sandbox.

Eight more locomotives were built with a 2-6-0 wheel arrangement and were numbered 2603 to 2610. They were nicknamed the Kruger class, after the South African Boer War leader Paul Kruger. Altogether the class was not very successful, with unsatisfying boiler performance and frequent fractures in the crank axles due to the long stroke. 2601 was already scrapped in 1904 as its wheel arrangement differed from the others. Most of the 2-6-0 locomotives had been withdrawn by 1906. At the same time, Dean had designed its Aberdare class and he re-used the numbers of the withdrawn locomotives for this class, possibly while re-using some parts of these locomotives.