 The remaining 17 complete kits at Woolwich were bought by the Southern Railway, and formed the basis of later locomotive classes such as the three-cylinder SR W class 2-6-4 tank locomotive.The prototype W class was produced in 1932 from N class parts with the addition of water tanks, a coal bunker, a rear bogie and a third cylinder between the frames.Woolwich also stocked a surplus of N class bogie components, and these were bought by the Southern for rebuilding the LB&SCR E1 class 0-6-0 tanks into the E1R class 0-6-2 tanks.