It is a great privilege for me to give the Twelfth Cierva Memorial Lecture. The title, which was suggested by the Society, might imply a mere recitation of past deeds. This would hardly be a fitting tribute to a great inventor like Cierva. Such men are usually impatient with the past and eager to explore the future. Accordingly I will deal with Bell's history as briefly as possible, and then discuss some aspects of helicopter rotor systems which have recently come to light.