Based on a French design, it was developed at the Royal Aircraft Factory, and built by six different British companies including Daimler, Rolls-Royce and Wolseley Motors Limited.

The heads were cast integrally with the cylinders, with the intake and exhaust valves set one above the other in an upside-down F-head configuration.

The engines featured a large diameter lightweight flywheel at the rear, enclosed in a cast housing.

From there it was gravity fed, via a gallery high on the right side of the engine block, to the main bearing caps, and then to the connecting rod journals by the centrifugal effect of the turning crankshaft.

Two passages cast into the cover took air-fuel mixture from the carburettor mounted at the bottom to a copper U-shaped inlet manifold mounted between the banks of cylinders, and the flywheel cover acted as a heat exchanger, preheating the fuel-air mixture.