Ariel 998cc square four 4G Mk2 motorcycle, designed by Edward turner, creator of the legendary Triumph Speed twin, the first Ariel square four was shown at the Olympia Motorcycle show in 1930. Conceived as an overhead-camshaft 500, the model grew to 601cc before a total redesign saw it emerge as the model 4G, with 995cc overhead-valve engine, in 1937. From the Estate of the late Pro Hart