Imagine you suddenly see a car careering unavoidably towards you on the wrong side of the road. You probably won't remember the bang or feel your head whiplash against the wheel and then crack on the side window. You may not hear the fireman cutting you out; in fact, you wake up one day in a hospital bed and wonder where you are, call a passing nurse and be told you are in hospital and that suddenly it is January, not November.

On your first day home you may find yourself exploding at your wife over some trivial incident. After a while, the children begin to steer clear of you. Some friends take you out to the pub, but their voices are drowned out in the cacophony so you slam down your drink and walk out. The next day one of the friends phones you up to ask if you got home alright, and you …