For the past seven years Dylan Cleaver has been at the frontline of reporting on sports-related concussion and its effects. His research has led him to agree - reluctantly, at first - with the world's leading experts who say children should not be exposed to contact sports. In the first of a three-part series on the science behind sporting head injuries, he explains what changed his mind.

There would have been a time, not that long ago in fact, when I would have dismissed the idea of banning contact sport for children as crazy talk.

I would have described it as a gross overreaction to a problem for which we still don't know all the questions, let alone the answers.

Yet the more I learn, and the more