Arthur has been rocking backwards and forwards for several minutes. At his feet is a drawing, identical to the one he drew a few hours earlier, and to others he will create again and again. His mother calls him. He takes no notice, as though he hadn’t heard. At 5 years old, Arthur is in his own world. Like more than 100,000 other children in France – and, according to some estimations, 650,000 other people including adults – he has autism.