'The Cierva Autogiro', 1941. The Cierva C.30 autogyro designed by Juan de la Cierva was built during the 1930s in Britain, France and Germany under licence from the Cierva Autogiro Company. Twelve machines built for the RAF entered service as the Avro 671 Rota Mk 1, and a few saw service during the Second World War. From "The Royal Air Force in Pictures", 2nd edition, by World War I flying ace Major Oliver Stewart. [Country Life Ltd, London, 1941]