[tim chapman]

yes i see now that the roll hinge action cannot be performed by the upper arm - thank you both

interestingly i found this today....

Horizontal hinging is a biomechanical action where the swinger rotates the back of the left hand leftwards so that the flat left wrist moves around to the left while remaining vertically oriented relative to the ground - in other words, the flat left wrist, which remains vertical to the ground, rotates to the left like a door opening. The AJ Bonar photo gives a swinger the impression that the left wrist rollover occurs at the level of the wrists/hands. However, that is totally incorrect! The roll over action must occur at the level of the left shoulder socket, and the entire left upper arm, left forearm, left wrist and left hand must rotate around to the left as a single unit - at the same rpm as the rotating clubshaft/clubhead. This explanation becomes clearly understandable if you consider the next photo of Anthony Kim's horizontal hinging action.

Image 1 shows Anthony Kim at impact and image 2 shows Anthony Kim at the end of the followthrough (defined as the time point when both arms are fully straight and all the power accumulators have fully released). Note that the clubface has rotated 90 degrees to the left so that the clubface (and back of the left hand) is vertical to the ground. What causes this 90 degree rotation of the back of the left hand and clubface? The answer is clearly discernible in the above photos.

Image 1 shows Anthony Kim at impact. Note that he has a strong left hand grip, which means that his flat left wrist/back of left hand is not quite facing the target at impact. Note that one can clearly see the back of his left forearm and note that the radial border of his left forearm is still facing slightly rightwards. Note what happens to his left forearm during the followthrough - the back of his left forearm rotates counterclockwise (as viewed from above) so that it faces the target at the end of the followthrough and the radial border of the left forearm faces the ball-target line. The left forearm's counterclockwise rotation is not due to any independent left forearm rotatory movements, but it is due to an external rotation of the left humerus (bone of the left upper arm) in the left shoulder socket joint (which has itself moved upwards during the followthrough phase of the swing - thereby making it easier for external rotation of the left humerus to occur naturally). Note that the left upper arm has rotated to the same degree as the left forearm, and that the left forearm has rotated to the same degree as the flat left wrist, and that the flat left wrist has rotated to the same degree as the clubface. That's what happens in a horizontal hinging action - the entire left upper limb rotates as a single unit at the same rpm as the rotating clubface, and the rotation occurs as if there is vertical hinge joint at left shoulder socket level thereby allowing the entire left arm unit to rotate horizontally like a door opening. If a swinger understands this biomechanical phenomenon, and understands that the left hand controls the clubface during the followthrough, then he can control the horizontal hinging action during the followthrough phase of the golf swing.

http://perfectgolfswingreview.net/power.htm

you can see the pics of Kim some 3/4 the way down (big article & quite a good one from what little i know of TGM)