The Fairmile D was a very large British MTB designed by Bill Holt and conceived by Fairmile Marine for the Royal Navy. Nicknamed "Dog Boats", they were designed to combat the known advantages of the German E-boats over previous British coastal craft designs. Larger than earlier MTB or motor gun boat (MGB) designs, the Fairmile D was driven by four Packard 12-cylinder 1250 horsepower supercharged petrol engines and could achieve 29 knots (54 km/h; 33 mph) at full load. The boat carried 5,200 gallons of 100 octane fuel for a range, at maximum continuous speed, of 506 nautical miles.