Arthur Rowledge, one of Napier's chief engineers and the designer of the Napier Lion engine, became fed up with management and left for Rolls.[4] In this one move any Napier design effort ended while Rolls' received a boost. Applying every known advance since the D-12 was introduced, Rowledge designed the new engine to use supercharging at all altitudes, allowing it to outperform naturally aspirated engines by as much as they were willing to increase the boost pressure.