 Maunsell enlisted the help of former GWR engineer Harold Holcroft, who suggested that a 2-6-0 wheel arrangement would allow the class to run on the poor-quality track in north Kent.This arrangement allowed for a longer wheelbase with leading axle to permit greater stability at speed on tight track curves, which had constrained the size of locomotives operating on the SECR.A longer locomotive could also accommodate a larger boiler than an 0-6-0, giving the N class sufficient power to avoid double-heading of locomotives on heavier trains.