[1] In late 1925 and early 1926, the Royal Aircraft Establishment (RAE) published a series of papers by Harry Ricardo on the sleeve valve principle.

The main advantages over the traditional poppet valves was better volumetric efficiency and the ability to operate at higher rotational speeds.

Roy Fedden, Bristol's primary engine designer, became interested in the concept and by 1927 he had constructed a working two-cylinder V as a test bed, with the idea of developing it into a V-12.

The first production versions of the Perseus were rated at 580 horsepower (433 kW), the same as the Mercury model for that year, which shows that the sleeve system was being underexploited.

It was in these designs that the advantages of the sleeve valve were finally put to good use and by war's end, the Centaurus was one of the most powerful engines in the world.