Pendulum (1968) av John Christopher.
Enligt en recension på Googles :
A failing economy, rising permissiveness, youth violence and rampant disorder lead to the fall of government in the UK and rule by mobs of youth motorcycle gangs. An upper middleclass family suffers deprivations and the occupation of their home by one of these gangs as the pendulum of society swings away from disorder to the rise of a religious brotherhood that soon takes on the gangs and creates an equally unappealing future.