This Stephenson Class were eleven 0-6-2T locomotives introduced into traffic in 1898 designed and built by Robert Stephenson and Company for the Port Talbot Railway. They predated the somewhat similar but larger Rhymney M class by six years.They were successful designs ideally suited to hauling coal trains a relatively short distance. Four of the class were nevertheless quickly sold two to the Rhondda and Swansea Bay Railway in 1901; and two more to the Neath and Brecon in 1903.