Castle Three / Castle Four (United Kingdom)

Castle Motor Co. Ltd was a British automobile manufacturer based in Kidderminster, Worcestershire, active from 1919 to 1922. Founded by brothers Stanley and Loughton Goodwin, the company emerged in the aftermath of World War I, leveraging their experience in manufacturing military components such as shells and gun carriage hubs. The Goodwins aimed to meet the growing postwar demand for affordable automobiles, opting to produce a three-wheeled vehicle characterized by a single rear wheel.

The Castle Three, the company's primary model, featured a four-cylinder engine, which was notable at a time when most competing three-wheelers utilized two-cylinder engines. Initially, the first twelve units were equipped with 1,094 cc Dorman engines, after which the company transitioned to using 1,207 cc engines sourced from Belgium's Peters. The vehicle employed an epicyclic gear transmission system, with power delivered to the rear wheel via a shaft. While the epicyclic transmission remained a feature throughout the model's production, some later examples, including one of the two known surviving vehicles, were fitted with proprietary three-speed gearboxes.

The Castle Three was well-received, as evidenced by the 2,300 orders placed at the 1919 Olympia Show. However, production faced challenges, and only approximately 350 units were completed before the Goodwins sold their factory to a local carpet manufacturer. A prototype for a four-wheeled model, known as the Castle Four, was developed but never entered production. The brief existence of Castle Motor Co. Ltd highlights the difficulties faced by many small manufacturers in the early 20th century automotive industry.