Ariel Square Four motorcycle, 1959.
© Science Museum / Science & Society Picture Library
Ariel began producing bicycles in the West Midlands in 1870, and in 1898 made their first powered vehicle, a tricycle using a de Dion engine. The company's best known motorcycle was the Square Four, designed by Edward Turner and first introduced in 1931. Named after the number and configuration of its cylinders, the Square Four was initially a 500cc machine, but the engine capacity was increased to 600cc in 1937, and the final version brought out in 1954 had a 954cc engine. In total, Ariel produced over 15,000 Square Fours, but in common with most of the British motorcycle industry, the company struggled to compete with Japanese imports in the 1960s, and closed in 1967.