Thomas Harrington decided to go into car manufacturing in 1961 because of a declining bus market, and also because it is quicker to build a car and therefore to generate income. Their fibreglass technique learned through moulding parts of coach bodies helped them to create the Harrington Alpine fastback. Harrington offered this expertise to Rootes for their Alpine Le Mans programme. A Harrington Le Mans GT won the Index of Thermal Efficiency at the 1961 Le Mans 24 hour race, and as a result Rootes sanctioned 250 replicas to be made, most of them sold in North America; this car did not have rear fins. The 'Series C' Harrington Alpine was launched in October 1962, still built on the Alpine series II body, but that was about to be replaced by the revised Series III Alpine wqhich required different mouldings. This led to the launch of the 'Series D' in January 1963 which could be ordered on the finned Series III Alpine, or the finless series IV, but only about a dozen were made. Harrington also modified 3 works Sunbeam Coupes for the 1962 and 1963 Le Mans 24 hour race, giving them Kamm tails. A change of board makeup within the Robins and Day group which had taken over Thomas Harrington in 1961 led to disinterest in the Harrington Alpine project and it declined into cessation in 1965.