Europe, whether you think of it as the EU or as a collection of sovereign states, faces the most massive demographic challenge in its long history. On the one hand, the population of native Europeans (white, post-Christian) is declining, most obviously in Germany, Italy and Spain. On the other, millions of would-be immigrants from Africa and the Middle East are knocking at the door, determined to get in.

They may die in the attempt. The water around their sunken boats may turn the Mediterranean red with blood. But they will not stop coming.

Torn between their instinct for self-preservation and their need for cheap labour, the peoples of Europe have formed into two camps. The first, small, but socially liberal, insists that all those who wish to come here should be welcomed and then woven into the rotting fabric of our society. The second, much larger and increasingly angry, is rising up, demanding that the shutters be brought down and the drawbridges raised.

Governments, as ever, are resolutely two-faced on the issue. They don’t want to be seen as aloof or uncaring, or racist. But they can also see what is going on and what their voters think about it. Having no solution to offer, they prefer to believe that other countries, preferably with borders far removed from their own, should bear the brunt of the burden.

In France, Emmanuel Macron is walking a fine line – something he is adept at but may yet betray him. He has openly criticised the new all-purpose coalition in Italy for turning away the rescue ship Aquarius, with its human cargo of 630 asylum-seekers, most of them from sub-Saharan Africa. But, simultaneously, he has made it clear that he has no intention of opening French ports to such riff-raff. Given that Malta also refused to take them in, those on board the Aquarius, operated by SOS Méditerranée and Médecins Sans Frontières, found themselves in a bit of a jam. It was only when the newly-emerged Socialist Government of Spain, led by Pédro Sanchez, stepped up unexpectedly, offering them safe haven in Valencia, that the immediate crisis was brought to an end.

But as one crisis ends, another begins. Sanchez not only allowed in the Aquarius 600, he also announced that he was considering removing the razor wire fences and other obstacles that surround Spain’s two north-African enclaves, Cueta and Melilla, thus potentially opening the floodgates to large numbers of intending immigrants seeking a shortcut into Europe.

The Spanish people have seen what happened in Italy when previous governments in Rome went along with the EU policy of admitting those who, one way or another, had successfully made the Mediterranean crossing. Italy, and Italy only, was left carrying the can. Already there have been calls in Madrid for the new Government to make clear that it is not ready to throw open its doors to all comers.

Germany, which three years ago admitted some one million asylum-seekers, the majority from war-torn Syria and Iraq, is currently re-evaluating its strategy. The rise of the far-right AFD party and the near-defeat in last year’s federal elections of Angela Merkel’s CDU have resulted in a stand-off between Merkel and her interior minister Horst Seehofer, of the Bavarian-based CSU. While the Chancellor is still prepared to reach out to help bring relief to Italy, the CSU, backed off-stage by the AFD, are saying enough is enough. Seehofer opposes the admission of Turkey to the EU. He rejects the idea that Muslims can be part of German culture and he wants to close Germany’s borders to practically all non-EU arrivals. He is not alone in this.

To Germany’s east, the so-called Visegrad countries have made it abundantly clear that under no circumstances will they allow Muslim or African immigrants to enter their territory. Hungary’s prime minister, Viktor Orban, has led from the front in his determination to keep his country white and Christian, but Poland, the Czech Republic, Slovakia … and Austria, are no more than a step behind. Brussels may huff and puff, but there seems to be little the centre can do when the centre itself is increasingly perceived as no more than a liberal redoubt, about as secure as Constantinople on April 5, 1453, on the eve of the arrival of the Ottoman host.

The disquiet openly displayed in the East finds its echoes even in the EU’s Western heartland, where in the Netherlands, Belgium and Denmark the sense is growing that Italy has a point and that Europe cannot be the home for everyone in the world who would like a higher standard of living than is available in their home countries.

The dilemma is stark. If Europe committed to take, say, another million refugees and economic migrants over the next five years and then call it quits, that would probably find favour across the EU. But that is not going to happen. Instead, every time a boat lands in Italy, or Malta, or Spain, or Greece, another sets sail. Unless something changes, the sequence, logically, will never end. There can hardly be an individual under 25 anywhere in Africa or the Middle East who would not rather live and work in Germany, or France, or Sweden than in the country of their birth. And given that the population of Africa in particular has doubled in the last 30 years and is expected to double again by 2050, the demand, and the pressure, on Europe can only increase.

Britain likes to imagine that it can somehow stand back from the crisis, watching it from afar, safe behind its moat. This is a nonsense. Leaving the EU may taper back the number of Poles and other EU citizens streaming into the UK. But by far the greater demographic threat is posed by the millions, even the hundreds of millions, of desperate young people from the developing world who are determined to claim a better life in Europe, many of whom, like the Angles, Saxons and Jutes of ancient times, will cross the Channel by any means possible and over time make their home in England.

If ever there was fertile ground for the growth across Europe of neo-fascism, this is it. What the EU’s leaders come up with to stem the tide and “take back control” of their borders, while at the same time retaining a spirit of kinship and racial and ethnic tolerance, may well determine the future of our continent for the next 50 years.