We all know we need immigrants. They do the jobs we cannot do or will not do. But how many and on what terms? If we don’t get it right, Brexit – in whatever form it takes – could end up being for nothing.

Meanwhile, the shocks just keep on coming. According to the latest figures, there are currently 411,000 Romanians living in the UK – or at any rate there were at the time of the last count. 411,000! That’s more than six times the number of British troops who landed in Normandy on D-Day. Given that the total has increased by 25 per cent since the referendum, it would be reasonable to assume that if and when we drive off the EU cliff edge next March 29, there will be a total of around half a million, including children and other dependants – enough to populate a city the size of Bristol.

Will they all be sent packing on March 30? Obviously not. But what will happen? Boris Johnson says immigration will continue, just not as rapidly as before, with more from the Commonwealth than from Europe and with British officials keeping score. So is that alright then? Is that what was meant by taking back control?

The talk up to now has been vague in the extreme. Ideally, we are told, the only new arrivals to be encouraged after the transition phase of Brexit will be those with certified skills that can be matched to known shortages in the labour market. But given that the skills gap in the UK manufacturing sector is likely to last at least another ten years, it is hard to see how immigration can possibly be restricted to the “tens of thousands” until long after Theresa May, and for that matter Jeremy Corbyn, have long since left the scene.

Immigration, in any case, tends to take on a life of its own. It doesn’t seem to matter what rules and monitoring systems are put in place, the result is the same – a steady stream of new arrivals, along with demands for the admission of family members and/or refugees and asylum-seekers.

When just a single Romanian flew in to Stansted on the morning of January 1, 2014, taking advantage of an end to previous restrictions, we were assured that fears of a Romanian “swarm” were well wide of the mark and that the few thousand who would most likely show up over time would be highly-skilled and linguistically competent. In fact, the numbers began to take off almost immediately and have continued to rise ever since, such that in just four years Romanians have become the second-largest EU immigrant group after Poles, well ahead of the estimated 175,000 arrivals from the Baltic states and the 50,000 or so from the Czech Republic.

It would be fair to say that most of the those who have moved here from the former East Bloc are decent, hard-working people who just want better lives for themselves and their families. To characterise East Europeans, and Romanians in particular, as criminally inclined, is just plain wrong. That is not the issue, or shouldn’t be. The real question is, at what point is enough enough? When can we put up the Britain is Full sign without being labelled racist or xenophobic?

England is already one of the most densely-populated countries in the world, more tightly packed than India and with three times the number of people per square kilometre than either Poland or France. The Tories are talking about building an additional 300,000 homes a year and putting the squeeze on the country’s greenbelts. London’s population is forecast to reach 9.5 million by 2050. Will our expansion only end when we finally explode?

We have, of course, been down this road before – and I don’t mean the response to Enoch Powell’s Rivers of Blood speech. In 2001, when Tony Blair was still widely thought of as a responsible and progressive leader, a total of 60,711 Polish citizens were officially registered as living in Britain. Eighteen years on, the number has increased 17-fold, to in excess of one million, more than half of whom live in London and the South East.

But it is not just the UK that is affected by the demographic flood. Across the Channel, a total of 350,000 Poles have settled in France since 2004, while in Germany, where no formal records are kept, the figure could be as high as half a million. Some 110,000 have settled in Italy, and 60,000 in Spain. The three Benelux countries between them are home to more than 210,000, while Norway, not a member of the EU but subscribed to the Single Market, recorded a total of 72,103 as long ago as January 1, 2012.

At the same time, some 1.2 million Romanians are said to have put down roots in Italy, and another 675,000 in Spain. Germany is host to 650,000.  Only in France, where there is a strong aversion to people perceived to be of Roma origin, has the tide been resisted. Just 20,000 Romanians are believed to have successfully settled in France since 1990.

Note that I haven’t mentioned the discomfort Nigel Farage feels when he hears commuters talking foreign on trains, or the dilemma of the people of Boston, in Lincolnshire, having to face up to the fact that 29 per cent of the town’s residents are from Eastern Europe, turning their local hostelries into the Pubs of Babel. Nor have I referred to the number of French citizens who have moved to London in recent decades, put at around 160,000, or the 130,000 Germans. And I am, of course, only talking about immigrants from the EU. We can take it as read that a million or more Indians, Bangladeshis, Nigerians, Somalis and others are already plotting their arrival as part of Britain’s New Look immigration scheme. My point is that while the UK is the destination of choice for a high percentage of East Europeans and others, never at any point – other than through the referendum – were the British people asked if this is what they wanted.