When it all began, in his third year of secondary school, we were not immediately suspicious that Ben was smoking cannabis; more concerned about him generally. We knew something was very wrong, but it was hard to pinpoint what, exactly, because the problems were so many. He was failing at school and no amount of discussion with teachers helped. He began to lose interest even in sport: his passion. He was disorganised, confrontational and furiously angry. He changed friends, hanging out with the same few who seemed to do little more than maraud about London parks. If we tried to control him, removing his phone or Oyster card, it caused terrifying rows.