The routine had already been rehearsed. A fight with the snake Nagini was supposed to send Harry Potter flying. And it certainly did that. David Holmes, Daniel Radcliffe’s stunt double, felt the impact, and it hurt. But that was the nature of stunt work. He was always taking a knock, and showing off another bruise.
The next day the team came back to perfect the routine. It still wasn’t quite as spectacular as hoped. So they did what they’d done hundreds of times before: added more weight to the pulley system that would launch Harry so that he would fly through the air faster.