Why shouldn't Britain's border be in Britain? Wasn't that why Kent voted Leave?
More broadly, British withdrawal from the EU would not affect this one little bit. It is a bilateral treaty.
But such is the difference between the Tory and UKIP areas that voted Leave, and the Labour, Lib Dem and Plaid Cymru areas that swung the referendum by also doing so.
Labour areas have far more politicised populations; far more people in them watch the news, for example.
That is true even of neighbouring parts of London. It has always been massively so between, most famously, the North East and the South East.
There is a reason why Hollyoaks, while ostensibly set in Chester, is full of people with nearly, but not quite, London accents. The makers know who is watching it instead of, say, Look North. And they know who is not.
The Tory and UKIP vote is arguably the leading section of the electorate at large where immigration is concerned, being particularly willing to lead voters in general to the stake on that issue, about which there is undeniably very widespread concern.
But the Number One issue like that in Britain is always the National Health Service, where it is the Labour vote that has the leading role.
In any case, the EU has never really had awfully much to do with immigration. It has, for example, literally nothing to do with the Calais jungle. But, being less politically aware, the Tory and UKIP vote does not realise or understand that.
Led by, or at least from within, the Labour Party, the trade unions, and the wider Left, the popular demand for the United Kingdom to withdraw from the European Union would begin in earnest if and when the EU ever became a threat to the NHS.
That had been about to happen, under TTIP. Now, however, it looks as if there is not going to be any TTIP. So, that's that, then.