For years, immigration was the issue that dared not speak its name in British politics. Now, as we have seen during the week our three main parties presented their manifestos, it is of central importance to anyone hoping to get elected. Whether it be the arrival of cheap labour from central Europe or of desperate souls on tragically unstable inflatable rafts from Syria, every politician needs a strategy.

Ironically, though, this is not the immigration that will most shape our lives in the coming years. Just as it has become politically acceptable to discuss immigration, we are looking in the wrong direction. If we are not to be blindsided by mass migration once again, we need to look elsewhere.

Typically, migratory flows reflect wide themes beyond the control of any one country. For migrants, technology can make the difference between suffering at home and taking a risk abroad: in the mid-19th century, the potato famine encouraged between one and two million Irish to make the journey across the Atlantic in search of a new future. What allowed many to leave, however, was the fact that a berth across the Atlantic was then far cheaper than it had been 50 years earlier, thanks to improvements in ship design.

The utterly impoverished are usually marooned, but a little economic improvement means they can afford the journey to a possibly more fruitful life elsewhere – one reason why so many still-poor Italians and Spaniards headed to Argentina in the late 19th century.