We all make mistakes as parents. Of course we all make mistakes all the time, whatever we are doing in life. But somehow the mistakes we make as parents bite deeper, wound us more. They are harder to shake off, tougher to leave behind. Maybe it is because we know how absolutely our children depend on us, how completely they need us, how utterly they trust us, and how completely they rely on our judgement.A few days ago, in a desert in the United States, a father and mother made a terrible mistake, a colossal miscalculation with appalling consequences. Keen travellers, adventurers, people who sound full of joie de vivre and with an extraordinary zest for living, Ornella and David Steiner set off to take their son, Enzo, aged nine, to visit a monument in New Mexico. It was sweltering, and t