Speaking of impact, I like what Jack has to say about it in his book Golf My Way. He writes:
"IMPACT. By now the 'lever is unhinging' as my wrists and right arm start to straighten. The clubhead, fully 'released,' is whipping toward the ball at maximum speed.
My preplanning for this critical moment will have centered on four factors: 1. Keeping my head where it's been all along--behind the ball.
2. Swinging the clubhead through the ball toward the target--not to the ball.
3. Keeping the left arm straight and travelling directly toward the target.
4. Avoiding any independent turning or twisting of the club with my hands and wrists.
And at impact itself? Well, I am still accelerating, still hitting. I am 'down' on the shot. I am trying to deliver the clubhead solidly and accurately to the ball..."
I find this description of impact, and Jack's four factors, very enlightening. I can see in my mind's eye Jack, in his prime, delivering the clubhead at impact. It was a thing of beauty. That poor ball knew it had been well and truly thumped when the Golden Bear hit it.