These ten locos, built in 1914, discarded the old Barry standards and were a bigger loco overall with a much bigger boiler and a very large bunker. They were generally considered successful with the exception of a serious and strange flaw. When running forwards the rear coupled wheels had a tendency to switch points as they passed through them, sending the trailing bogie down the other branch. In reverse, they were fine. Naturally this resulted in an immediate derailment, and this was usually coupled with a fracture of a main water distribution pipe. This lost all the water, meaning the fire had to be immediately thrown out.
On absorption, they were numbered 1347-1355 and 1357 and given diagram B. Four were rebuilt in 1922 with Standard 4 boilers, the first Welsh class to receive such a major change. This was allocated diagram C. In 1926, with the loss in traffic resulting from the General Strike, it appears the GWR lost patience with their reluctance to stay on the track and all were scrapped in short order.
1356, by the way, was allocated to an 0-6-0T locomotive that had been built for the Severn and Wye Railway, had been taken over by the GWR in 1895, rebuilt by the GWR in 1896, sold to the Alexandra Docks and Railway Co in 1912, and then resumed its 1895 number when it came back to the GWR at the grouping.