CALAIS, France—For years, France and the UK have been locked in a tense back-and-forth over how to handle the steady flow of illegal immigrants across the English Channel, between Calais and Dover, twin towns separated by just 20 miles of sea.
Inflatable boat crossings—already ferrying more than 30,000 people this year—are now a defining political issue in Britain and France, testing both governments’ promises to take back control of their borders.
