[1] In that year the 205 class 0-4-2T locomotives were introduced, for use on the London suburban passenger services.
[1] They performed well, but their capabilities were restricted by their small fuel and water capacities,[2] so after twelve were built, Cudworth produced an enlarged version of the design.
With the fuel capacity raised from 0.75 long tons (760 kg) to 1.25 long tons (1,270 kg) and the water capacity raised from 690 imperial gallons (3,100 L) to 850 imp gal (3,900 L), the extra weight and length needed behind the cab required adding an extra trailing axle, producing an 0-4-4T - the first of that wheel arrangement to be built for an English railway (the first Scottish railway to use the 0-4-4T wheel arrangement was the Caledonian Railway, in 1873).
[2] Only one batch (of seven) was built in 1866;[6] there were troubles with the bogie, and so when more were required Cudworth once more used the 0-4-2T type, producing the 73 class.
[7] Under Stirling's locomotive classification scheme of September 1879, they formed Class J.