IMMIGRATION HAS BECOME one of the great defining, dividing issues of our time. In Europe, it is helping to overturn governments, dissolve old political certainties, spawn large populist movements and, in Poland and Hungary at least, perhaps destroy democracy itself. Anxiety about immigration drove Britain’s vote to leave the European Union and the return of the far right to the German parliament for the first time since the Nazi years. A poll last year found that a majority of respondents in all European countries bar Finland were either ‘worried’ or ‘very worried’ about immigration.

Not just in Europe. In the United States, the oldest and largest immigration nation, Donald Trump’s promise to substantially cut migrant numbers, above all by building a wall to stop people entering from Mexico, helped to elect him president. Around the world, the mass movement of people divides those who feel more at home with globalisation from those who fear being left with no comfortable home at all. In a recent report, Balanced Migration: A Progressive Approach, Harvey Redgrave of the Tony Blair Institute for Global Change finds ‘barely a liberal democracy in existence today that has been untouched by political debate over immigration’.