Can Britain ever bring net migration down to the tens of thousands?

If you want net migration to come down how on earth do you do it?

The talk of relaxing non-EU migration and tightening EU migration post-Brexit begs a lot of questions.

Non-EU migration is itself above the 100,000 cap that David Cameron promised and which, you might think, for those most concerned about migration, is a cap they would have in mind too.

Then there’s the issue of what do you do with EU migration.

What would happen if you applied the same visa criteria on EU migrants that currently apply to non-EU migrants – a salary above £21,000 and a graduate level job.

The Social Market Foundation have given us a sneak preview of some work they’ve done on what this would mean. They’ve found 1.6m people born in the EU are working as employees in the UK (so that’s excluding the self-employed). They’ve dug into this sizable cohort because it gives you salary and job information. If you only keep the people who qualify under the non-EU visa criteria, 1.4m wouldn’t pass the test, 88% of EU born employees currently in the UK wouldn’t pass the test.

Iain Duncan Smith for Vote Leave says an independent Britain would decide its total cap and its specific needs and devise some tests accordingly. None of this would present a problem.

Elsewhere the campaign was getting even shriller.

Vote Leave’s Facebook page now has now uploaded an attack video which uses Mr Cameron’s promises before his EU negotiations with Brussels. It says that the Prime Minister’s “deal with the EU did nothing to take back control of immigration” and that he now wants to “pave the road” for Turkey to join the EU.

That will go down fairly badly in No. 10.

But then allies of No. 10 seem to have helped to make sure that Boris Johnson could barely get heard on the high street in Winchester today. There was the usual affectionate mobbing and selfie-hunting by admirers but also a loud posse of pro-EU campaigners, one in a gorilla suit, some shouting “liar” throughout Mr Johnson’s stump speech.

At one point as he walked down the street Boris Johnson snapped “just shut up” at the most persistent campaigner.

Even when purdah kicks in at midnight tonight, the Prime Minister’s visits will remain carefully controlled to the point of being sterile. Leave campaigners fell they have a better look with their man walking unprotected, mixing with the people on paye out on the streets. One on the campaign said they thought it was an attempt by Remain to drive them off the streets and a sign of the potency of their approach.