Despite having one of the strongest navies in the world, the Royal Navy knew they needed a fleet of high-speed fighting ships to challenge enemy warships and to take a heavy toll of enemy merchant vessels. Mainly relying on stealth, speed and manoeuvrability, the Vosper company had been designing such craft since the early 1930s, with the Vosper 73ft Motor Torpedo Boat being a later development of those earlier vessels. Powered by three Packard engines, the Vosper was capable of speeds over 40 knots and in this variant, featured four 18-inch deck-mounted torpedo tubes, an Oerlikon 20mm cannon and up to four Vickers machine guns.