Man Utd boss Ferguson challenges boffins over Ronaldo free-kicks
"He practises all the time, 20 or 25 minutes after training, there he is with the balls. Wall up, bang, bang, bang, bang. He takes about 30 kicks every day, so . . ."
However, University of Manchester professor Robin Marshall believes: "It's intrinsic skill combined with exploiting chaos. When it's turbulent, imperfections in the ball will come into play, you can't predict the outcome. The ball isn't a perfect sphere, it will do funny things, but I yelled out in amazement when he scored. There was no spin. Gravity and the ball's imperfections brought it down and to the right."