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. Anstey-link plunger rear suspension became an option in 1939, but would not be offered again until 1946, when a telescopic front fork replaced the previous girder type. An exercise in weight shedding saw the cast-iron cylinder head and barrel replaced by alloy components for 1949, the revised model, now capable of 90mph-plus, being known as the Mark 1. Introduced in 1953, the 'four pipe' Mk2 with redesigned cylinder head elevated the Square Four into the league of genuine 100mph motorcycles. Square Four production ceased in 1959, along with that of all other Ariel four-strokes. To date, the innovative Ariel Square Four remains unique in motorcycling history; a true 'gentleman's motorcycle', this refined yet characterful machine retains an enthusiastic and loyal following, and is highly prized by discerning enthusiasts.
Last taxed for the road to the end of October 1968, this Ariel Square Four is offered for restoration and sold strictly as viewed. (It should be noted that the engine number appears to have been over-stamped). The machine is offered with old-style continuation logbook (issued 1966).