Not so long ago, those of us who sensed the heavy tread of middle age, with its tightening bear hug of responsibility, might have envied the young: their insouciance, their freedom, their ability to carouse all night and sleep it off until midday. Not any more. I look at teenagers now, their little brows already furrowed with worries about extortionate house prices and soaring university fees, and I feel sorry for them.