In an ideal world, hard choices could be avoided. It would indeed be marvellous if the sort of high-density mixed development that rejuvenated the heart of Barcelona could be transplanted to inner-city Britain. Yet we are deluding ourselves if we think that this is likely in the short term. It took decades for the cities to be hollowed out, and it will take just as long to restore them to their former glory.

Until then, the choice is either to accept higher property taxes and build more homes in the places that people want to live, or what Barker calls "increasing problems of homelessness, affordability and social division". It's not good enough to suggest this is only a question of building more social housing, since such accommodation that is not part of a mix of housing types rapidly becomes a ghetto. Nor is it acceptable to suggest that demand and supply are balanced by squeezing families into empty flats above chip shops. Unless, that is, we would be willing to have the smell of fried cod drifting through our own homes.