One example of the Horsley, serial number J8620, was equipped with an Armstrong Siddeley Leopard 14-cylinder twin-row air-cooled radial engine. The Leopard was the most powerful radial engine in the world at the time and in consequence promised much better performance.
A specific model of the Horsley, designated as J8620, was equipped with the Armstrong Siddeley Leopard, a 14-cylinder twin-row air-cooled radial engine that was the most potent of its kind at the moment. This led to enhanced capabilities.