[strav]

This is Johnny Miller's view from 1976. Not claiming it is correct but may be of interest to some.

The various parts of the body do not complete their backswings at the same time. They wind up sequentially. The knees and hips will complete their backswing before the shoulders, the shoulders will complete their backswing before the arms, and while most of the wrist cock is done early in the backswing, there is a tad more wrist cock at the top. This additional wrist cock occurs due to the pull of the clubhead on the hands as the club finishes its backswing, and also because of the pull of the left side which initiates the downswing. The shaft bending in response to the change of direction causes the wrists to achieve their “maximum” cocked position.
In fact, the left leg makes its move into the downswing just as the hands and club have completed their backswing. Then there is a time lag before the pull initiated by the left leg travels up the left side and is felt in the hands. This time lag is the pause you feel. But it is a vital feel to have because it’s proof to you that your change of direction is correct.
You begin the downswing in the same way that you started the backswing, by a move from the knees. To be more precise, the knees move laterally toward the target. The reasoning is the same as on the backswing, too. On the backswing, you had to shift your weight to the right foot. As you start down, your weight is still on your right foot, and, as has been said, you must have your weight on the left foot in the downswing. So the knees go to work. The left knee pulls to the left and the right knee drives right behind it with a push off the right foot.
I want you to be quite certain on this point. It’s the knees that start the downswing, not the hips. So many teachers, and well known ones, too, still insist on a “lateral shift of the hips” initiating the downswing. This is a bunch of bunk. In reality, you can’t turn your hips without the legs initiating the movement.