According to Arthur Rubbra's memoirs, a de-rated version of the "R" engine, known by the name Griffon at that time, was tested in 1933. This engine, R11,[2] which was never flown, was used for "Moderately Supercharged Buzzard development" (which was not proceeded with until much later), and bore no direct relationship to the volume-produced Griffon of the 1940s.