In 1954/1955, due to falling sales of motorcycles, the prototype 3-wheeler powered by a Vincent Rapide 998 cc engine was produced. Some years later, the vehicle was named "Polyphemus" by its owner, Roy Harper. To keep development and production costs low, it used a parts-bin approach, including pieces from Vincent motorcycles, as well as wheels which came from a Morris Minor. The body was made from 16-gauge aluminium. With the standard Rapide engine, "Polyphemus" could reach . Before it was sold, in the hands of Ted Davis, it achieved with a Black Lightning engine. The "Vincent 3-wheeler" was eventually sold to a member of the public for £500 – a high price for any vehicle at the time, especially for a vehicle with no reverse gear, self-starter or hood. The BMC Mini launched four years later at a price of £497.