You have to laugh, you really do.

After two years in which the outgoing President of the European Commission, Jose Manuel Barroso, was hailed as the fount of all authority on Scotland's place in Europe, suddenly he is condemned as another jumped-up eurocrat trying to take away Britain's freedom to control its borders.

Mr Barroso has pointed out to the UK Government that free movement of people is one of the founding principles of the European Union, and that there is no prospect of Britain being able to negotiate immigrant quotas.

Not so, says David Cameron, holding the threat of an in/out referendum over the heads of the EU. And he's "the boss" he said yesterday. So B-off Barroso - you'll take it or we'll leave it.

It could come to that. The last time David Cameron used his veto was in 2011 over the banking reforms to meet the financial crisis, and the rest of Europe just ignored it. Then, Mr Cameron had hopes of aligning with conservative-oriented newcomer states in central Europe such as Poland. But not over internal migration. This is not like other EU issues.

People wonder why the European Union is so keen on allowing free movement of people within its borders, and to understand you really have to go back to the origins of the EEC in the 1950s. This project was all about making war between Germany and France impossible and, bizarre though it may seem, that is still largely the project today. As Helmut Kohl said in the 1990s, even the euro is about "war and peace in the 21st century". (And, looking at Ukraine, maybe he had a point.)

If you have free trade and a common currency it is almost impossible for countries to go to war with each other. Almost, but not quite. Currency unions can break down, or come under intense strain as the eurozone crisis indicated. So the original project of the europeans was to mix people up as well as merge their economies.

This was expressed in very hard economic, free-market terms. It was argued that if you have free movement of capital and investment but not free movement of people there will be bottlenecks and inflation in the system. That's sort of true, but not hugely. There is, frankly, a problem with free movement from countries at very different stages of development as we have seen in Britain. The minimum wage here is not far off the average wage in Romania. Workers can come here and undercut British employees, live 10 to a room, and still send money back.

Actually, the EU foresaw this and did propose restrictions when the big expansion was mooted in the 1990s after the creation of the single market. But here's the thing. The biggest advocate of free movement of people back then were Margaret Thatcher and the Tories.

Indeed, John Major made it a principle of British membership that there had to be rapid expansion and absorption of the Central European countries. Back then Conservatives were rather keen on importing cheap Poles and Czechs to undermine UK trades unions.

But Europe's idea of free movement wasn't about economics alone. It was really about mixing up the nationalities of Europe so that language barriers could be broken down and national boundaries eroded. It was to create a European citizenry, and it has been hugely successful - especially among the young who now simply expect to move freely around Europe without border posts. Indeed, the idea of creating borders to stop free movement within the EU itself seems almost barbaric now to anyone in Europe under the age 40.

Ironically, the common language of this new young Europe is English. And hey ho - we're about to leave it. No you really couldn't make it up. This principle of free movement of labour, that we called for, is now so onerous apparently that David Cameron is threatening Brexit in order to end it. And take Scotland out too.

The paramount objective of British foreign policy right now is to keep Europe out of Britain.To erect border posts to keep out migrants. And they said that it was Scottish nationalists who were obsessed with borders.