When I first saw six-year-old Pieter, I noticed both his huge, inquisitive eyes and his deep, troubled frown. Pieter is prodigiously intelligent (Asperger’s syndrome was diagnosed two years previously) and also easily becomes very anxious.

Over the past few months, he had become highly fearful that something terrible was going to happen, with the effect that he no longer wanted to go to  school or to sleep at night...