The car, designed by Edmund Woodward Lewis (1870-1941) who had joined Rover from Daimler, had an unusual structure. Instead of the conventional chassis, the car had a backbone structure, formed by the engine crankcase, the gearbox housing, a rigid tubular propellor shaft housing, and the rear axle housing; the whole described as having a box girder section. The backbone frame, without bump-compliance at the rear apart from the tyres, was suspended from the front axle at just one point by a pivoted transverse leaf spring which made no contribution to transverse rigidity, and thus the whole remaining car rested on just three points, similar to the design of old, four-wheeled farm tractors.