In an article by A Harvey-Bailey, W Smith and M Houston they write of the three-speed Griffon:
"The final version of the two-stage Griffon was the RG3SML, which featured a three-speed supercharger having a first stage impeller of 14.3 in diameter, second stage of 12.25 in diameter and gear ratios of 5.752 (LS), 6.735 (MS) and 7.7 (FS). This engine was proposed for several applications under consideration at that time, for example the Martin Baker MB5 (Griffon 103, single rotation 0.451 ratio), Spitfire Mark 24 (Griffon 101 and 102, single rotation 0.451 ratio, Griffon 105, single rotation 0.51 ratio and Griffon 121, contra-rotating 0.4423 ratio) and Hawker F2/30 (Griffon 130, contra-rotating 0.4423 ratio), but none of these projects went ahead. Just prior to the end of the war, Supermarine were developing an improved version of the Spitfire to Air Ministry Specification F1/43 named the Spiteful, featuring a laminar flow wing, wider track undercarriage, and improved visibility for the pilot. The engine for this aircraft was originally the Griffon 70, a two-stage two-speed variant similar to the 60 series Griffon, but some of the seventeen aircraft built were fitted with the Griffon 101. In March 1949 the Spiteful prototype, powered by a Griffon 121, flew at the record speed for a piston engined aircraft of 494 mph. Development of the aircraft was overtaken by the arrival of the jet age and the RG3SML never saw active service. The laminar flow wing of the Naval version of the Spiteful (the Seafang), however, entered service on the Supermarine Attacker, the first Fleet Air Arm carrier borne jet fighter, powered by the Rolls-Royce Nene." and added "The Griffon 121 powered Spiteful achieved 494 mph in level flight, while the Griffon 66 powered Spitfire XIX achieved Mach 0.92 (620 mph) in a dive."
