Campaigners argue that there has been a growth in autism cases of ‘epidemic' proportions in the Western world over the past two decades - due to everything from vaccines and antibiotics to pesticides and diet. But the increased prevalence of autism is better explained by increased awareness and improved diagnosis, along with the broadening of the concept of autism, Fitzpatrick shows.

Instead of trying to fight the ‘environmental toxicity' of the modern world, parents should concentrate on fighting for the best possible education and social care for their children. But above all, they should interact with them, he says. Fitzpatrick argues: ‘Sometimes it is more difficult simply to spend time with our children than it is to pursue investigations and treatments.' He explains that children with autism may retreat into their own world. They may pursue obsessional rituals and challenging behaviours. ‘The very fact that it is so difficult to engage with children with autism underlines the importance of continuing to try', he writes.