"The trick is not minding that it hurts!"
The question is
"how did they do it?" I've pondered this for years and have examined the scene frame by frame. If I had ever had the chance to ask Peter O'Toole one question it would have been "how did you do it?" I'm convinced his answer would have been "in one take." I've come to the conclusion that he actually did it. No tricks. He probably did mind that it hurt but this was offset by a big paycheck and a breakout role.