A group of artists in California called Heavy Trash has launched a guerrilla war against gated communities, the self-contained housing estates that are walled off from the outside world but ring more and more American cities. In a stealth operation, carried out at dawn, a group of 20 architects, designers and urban planners deposited 12ft bright orange viewing platforms at the gates of three of Los Angeles’s most exclusive developments. Heavy Trash says that gated communities are the fastest growing type of housing development in the United States: more than eight million Americans now live in hermetically hived-off homes. The impact on the public domain is generally malign, of course – but remember this: the gates which keep us out also keep them, in.