In order to cope with the steadily increasing weight of express passenger traffic on the Southern Railway in the early years of Grouping, Richard Maunsell, the Chief Mechanical Officer, needed a locomotive that was more powerful than the King Arthur class, but one that would still conform to the various gauging and weight issues within the region and still be capable of hauling 500 ton trains at a speed of 55mph.The new Lord Nelson design had to fit within the profile of the King Arthur class and having previously used a Drummond four cylinder locomotive as a test bed, Maunsell altered the positions of the cranks on the Lord Nelson design to give eight exhaust pulses per revolution, rather than four.