The first batch of the N class proved successful in service, and few problems were encountered after settling-in. The Ministry of Supply drew up a contract for a second batch to the same specification – to be built at the Royal Arsenal, Woolwich. The government backing came as part of a proposal to nationalise the railways, which would require a standard fleet of locomotives to promote economies in production and maintenance. The nationalisation proposal was abandoned; instead, the government passed the 1921 Railways Act, which grouped the railways into the "Big Four" in 1923. Building of the second batch went ahead to retain skilled labour at Woolwich, but the fabrication of 119 boilers for allocation to the kits of parts was contracted-out because of limited production capacity at Woolwich and Ashford; the North British Locomotive Company built 85, Robert Stephenson and Company 20, and Kitson & Co. 14. By 1924, the prefabricated components stored at Woolwich formed 100 complete N class kits for purchase from the government.