Simultaneously, huge numbers of non-EU immigrants are opting for naturalisation. In 2011 a total of 177,878 became British citizens. India was top with 26,290 and Pakistan was second on 17,641. The other countries in the top ten were Nigeria, the Philippines, China, Iraq, Iran, Bangladesh, Sri Lanka and South Africa. The total figure for 2011 was not untypical. Commonwealth nationals resident in Britain can vote in domestic elections without naturalising but nonetheless, over a decade or two, an enormous number of immigrants will have earned the right to vote. 

As Paul Collier makes clear in his new book, Exodus (Oxford, £20), these changes are bound to have a serious cultural impact and it is daft to pretend otherwise.

Yet this need not automatically benefit the Left. If the Conservative party could make a clear appeal based on the themes of hard work, self-reliance and interdependence, it might win over migrants and their children, as well as resonate with indigenous voters who are attracted by similarly aspirational themes.

It would certainly be a mistake to presume that migrants who are ambitious enough to cross continents, or leave behind established communities in their homelands, in search of self-improvement, are here first of all for the welfare and public services, although they do consume those services as well pay tax. The experience so far suggests that the overwhelming majority are extremely determined to work. The Poles are so productive and diligent that they put many of the natives to shame. Enter a branch of any upmarket sandwich outlet, or visit a pub in London, and you are highly unlikely to be served by someone born here. You are dealt with, efficiently and often with a smile, by an immigrant.

There is scope for cultural confusion, of course. Standing with friends at the bar of an old, proper pub in the City recently I suffered a communication failure with an Italian barmaid who may have been new. She explained: "There is lager, and there is bitter. Light and fizzy, or dark." I attempted to explain that there is something called pale ale, which is proper beer but lighter in colour. She shook her head slowly: "There is lager, and there is bitter." (She may have had a point as pale ale is not widely available on tap.)

Far more serious downsides are apparent, not least in terms of the impact on the younger part of the existing population. The UK's economy is recovering strongly, yet the country is carrying youth unemployment of around 20 per cent. Even though official figures suggest that this figure is now falling slightly as the economy revives, it represents a criminal waste of human capacity. Young Britons are losing the competition with migrants for jobs, let down by poor education, welfarism and the tyranny of low expectations. They are unable to keep up. 

Those youth unemployment statistics help explain the rise of UKIP. The party's leader, Nigel Farage, taps into a rich seam of discontent. He asks: how can it be that a country whose own youngsters cannot find work is allowing foreign labour to stream in and undercut wages?

It is a good question, but again it is too late. Short of the kind of lunatic and inhumane mass repatriation which would never be contemplated, there is no serious prospect of those who are here disappearing, particularly when the UK economy is forging ahead of the rest of Europe and there are employment opportunities. We are going to have to continue to find ways of living alongside each other.