 Despite making various modifications to the steam circuit on other Maunsell classes, Bulleid saw no reason to make such drastic alterations to the N1 class.As a result, the final set of modifications made under Southern Railway ownership was made after the Second World War and included the removal of superfluous smokebox-mounted anti-vacuum snifting valves and the replacement of the wide-diameter N1 chimney with the U1 type to improve draughting on the prototype; the standard N class chimneys of the other five were also replaced.The class was well-used by British Railways over both Central and Eastern sections between 1948 and 1962 and justified the fitting of Automatic Warning System (AWS) equipment in 1959 alongside the N class.