 He instead offered the WF class 2-6-4T as a suitable design that could be released due to the conversion of locomotives of classes BB (4-8-0) and C (2-6-2) to heavy shunting locomotives.The WF class was by now largely confined to shunting work, except for those allocated to the isolated Picton and Nelson sections.TGR agreed to purchase a batch of four WF class locomotives in 1939.