Improving housing is no solution when the occupiers have little chance of a local job. A sub-culture of bitterness and despair will return, dissipating any improvements. This could spill over into neighbouring, more buoyant areas.
Smaller towns are likely to suffer less because they have a more balanced structure. But it would require major government intervention today to prevent problems in the bigger towns getting out of hand in the next century. Ruthless decisions are needed about major surgery to cities, he says. Historic cores will survive because buildings are capable of regeneration and can generate a mix of uses. Other areas with good building stock will also pull through. The problems arise from gaps in between.
The apocalypse is already happening in the US. Mr McRae points to development of "edge cities" as white, middle-class professionals desert the inner areas to communities centred around shopping malls. Residents will provide their own services via an elected group. You would need permission to move in. This could be like Rome in Dark Ages or England after the Plague, where large parts of inner cities were abandoned. He cites the Detroit City Ombudsman in Detroit who has already suggested that sections of her city should be fenced off and returned to nature.
Mr Thompson similarly believes the UK could be returning to the era of walled cities, as affluent suburbs protect themselves from the chaos around, and that some inner city areas might be best turned into parks. The alternative is massive intervention - yet the trend is towards free-market forces.
Mr McRae insists that the UK will escape the worst of US experiences. This is because land values are much higher around city fringes, making the creation of edge cities less feasible. Government is also far more involved in UK city centres. They receive large subsidies and have better public transport.
Britain also has a different attitude to cities, treating them as places of entertainment and culture that deserve to be visited rather than avoided. The city fringes will be the main problem, as local authorities struggle to deal with vast and desolate estates of housing, racked by unemployment, lawlessness and despair.