Driving impression: Diesel Quads Diablo 850 ATV Diesel delight or diabolic disaster? Formerly trading as GHL, Anglesey-based Diesel Quads is a small company that has been quietly developing and manufacturing diesel ATVs for more than ten years. Its latest Diablo 850 model is produced in limited numbers so, although often referred to, not too many machines have been sold or made available for extended test rides. James de Havilland nabs one off the military