It is perhaps little wonder immigration is as politically charged an issue as it is, when you consider two things.
Firstly, as I wrote here, the numbers point to it being the stand-out UK social and demographic change of the 21st century.
And secondly, it is also one of the biggest and most transparent political failings, when you compare rhetoric to reality.
There were the projections made by Sir Tony Blair’s government two decades ago that allowing unlimited migration from central and eastern Europe would tempt modest numbers of people to move here – and huge numbers turned up.
In the 2010s, the Conservatives repeatedly promised to cut net migration to the tens of thousands a year, and repeatedly failed.
The numbers then rocketed after Brexit, the very act that meant UK governments were entirely responsible for immigration policy for the first time in a generation.
Most people miss most political debates most of the time, but some are sufficiently totemic they are not just noticed but make the political weather.
The arguments over immigration are one of them – and what I have just set out tells you why.
This is the generational context within which this prime minister’s promises perch.
It is a longevity of failure that senior politicians of various political persuasions privately accept – perhaps more so than any other single issue – has seeded a cynicism and a disillusion with how we are governed.
Sir Keir Starmer’s language felt like an acknowledgement of that central point: here was a Labour prime minister, a former human rights lawyer, claiming “we risk becoming an island of strangers.”
It is a phrase some, particularly on the left, regard as repulsive.
Others counter that it is a widely held perception which it is high time those in high office shared.
Labour wrestle with the many practical and political trade-offs around immigration policy, just as other parties in government have as well.
In practical terms, staffing care homes, building new houses – can these things be done without an influx of folk from abroad?
Interestingly, Sir Keir took issue with the long-standing view of many that immigration helps drive or at least prop up economic growth.
The other context here is the insurgency of Reform UK.
Nigel Farage argues, as he has for years and years, that politicians have been far too slow to get how much immigration matters to so many people.
Labour are acutely aware of Farage’s capacity to communicate in a way that resonates with those who feel successive governments have not just ignored them on this issue, but belittled and demeaned their views too.
That is why the prime minister is using the language he is now.
And there is another thing going on here too.
This is a week of muscular language and intent, firstly primarily on legal migration now, and in a few days on illegal migration too.
By next week the focus will switch to an anticipated new deal between the UK and the European Union, and within it, the likelihood of a youth mobility plan – meaning young people from the UK can travel more freely around Europe, and those from the EU can come here.
Ministers will insist this doesn’t amount to freedom of movement, nor immigration – because visits in both directions will be strictly age and time limited.
But you can be certain there will be a row about it.
These then are the short, medium and long-term reasons why the prime minister and his team know that their plan for delivering a sustained downward trend to the net migration numbers is absolutely crucial to their credibility.
