Manchester United boss Sir Alex Ferguson insists there's no mystery about Cristiano Ronaldo's amazing free-kick ability.

"All that stuff about hitting the ball in a certain spot in a certain way," says Ferguson, laughing. "There's no secret. The important thing is practice. It makes perfect, as I was taught in school. The boy practises every day, that's the reason he's so good. We go for a cup of tea and leave him to it.

"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."