They were originally intended for use on heavy coal trains from Trehafod but, as the B1 class proved more than adequate for the work, they were assigned to different duties.

The problem would only occur when the locomotive was travelling smokebox-first over facing hand-operated points, usually to be found in colliery sidings, marshalling yards and the dock area.

The rear coupled wheels, nearest the bunker, would force the tongue of the point open, causing the trailing bogie not to follow the driving wheels but to take the wrong road.

Several engineering solutions were attempted both on the locomotive and on the track to overcome the problem, but never fully successfully.

One story has it that they were unintentionally destroyed resulting from a clerical error at Swindon, but this has never been confirmed.