IT was the great mystery of the festive season.

Many had witnessed the occurrence but could not quite believe their eyes. Now at last the truth could be revealed. How had it been done? Why had it happened? Could such a deed of publicity-seeking brazenness ever occur again?

We refer not to Sherlock Holmes and his miraculous, ratings-generating return from the hereafter, but to Labour MP Keith Vaz popping up at Luton Airport on Ne'er Day. It can be bad enough arriving at Luton on the red-eye, but pity the poor passengers of the flight from Romania who exited the arrivals area to find the chairman of the Commons Home Affairs Committee, plus Conservative MP Mark Reckless, plus camera crews and reporters, waiting.

"My God," said an understandably overwhelmed Victor Spirescu, "I don't come to rob your country, I come to work. You open the border, I come to work, to make money, to go home."

As an "anything to declare" statement it encapsulated the credo of migrants down the ages. That it had to be stated at all in the middle of a three-ring media circus is testament to the tizzy in which England finds itself as January dawns and the door is opened to Bulgarians and Romanians.

One says "England" because it is nothing to do with us, is it? Regardless of the fact that these citizens of the EU can go anywhere in the UK, the matter seems to be regarded as something that has little to do with Scotland. Migration rows happen elsewhere. In Scotland, the door is always open and the welcome is perennially warm. If you can take a drink and take a joke, you are one of us. Wha's like us when it comes to welcoming people?

Like our respect for education and our steadfast belief that there is such a thing as society, it is one of those home truths held to be so self-evident it is not worth questioning. In this big country of ours there has never seemed a pressing need to talk about migration. In any case, you would be mad to do so. Migration has become the third rail of politics: to even step within a mile of it is to run the risk of being fried and accused of holding all kinds of unspeakable opinions.

Indeed, Scotland is apparently so at ease with migration, so far ahead of the game compared with the rest of the UK, that the country could actively take steps in the future to boost it. In the Scottish Government's recently published White Paper, taking control of immigration policy is listed as a major gain from independence. With an ageing population and a shrinking workforce, Scotland's Future states that "Scotland has a clear economic rationale for growing our population". While there is mention of a "points-based approach" and an immigration system that is "controlled, transparent and efficient", the bottom line is that an independent Scotland "will welcome people who want to come to work and live in Scotland". Give us your energetic, your solvent, your skilled masses yearning to earn a little bit extra. More so if you are a plumber willing to work on January 2.

It is a laudable aim, the kind that would fair make one proud to be a citizen of an independent Scotland. But it is also reasonable to assume that not everyone might feel the same. Much as it might make some uncomfortable to even talk about the subject, migration has to be as much a part of the independence debate as the currency, defence, the environment, and jobs. Migration is not an English issue. It is an EU matter, a global question, a topic that will shape nations for generations to come. Does such a pivotal concern really have no place in the independence debate?

One can understand the temptation to leave it off the table. The row over Bulgarian and Romanian migrants has been an example of dog-whistle politics at its worst. Never mind that they are EU citizens like the rest of us. Never mind that it is the law that they can live and work here. Never mind that the borders to other EU member states have been open for years, and many of those who wanted to leave have already done so. If they had been bankers, lawyers and architects there would have been no fuss at all; but given they are likely to be low- to no-skilled individuals it has been open season on their motives for coming here. Tales abound of internet message boards where advice on claiming benefits is traded like stocks and shares. The talk in certain papers is of an "influx" and a boom in begging. No wonder Laszlo Andor, the EU employment commissioner, warned the UK about appearing "a nasty country".

To criticise any of this is not to dismiss the concerns that exist. Concerns, it should be said, that are being fuelled in large part by ignorance. It is simply not known how many Bulgarians and Romanians will come to the UK because the Coalition Government will not publish estimates, having seen the Labour government get its numbers so wrong on east European migration. The think tank Migration Watch UK puts the figure at between 30,000 and 70,000 people a year for the next five years. Whatever the number, there are clear implications for housing, health, education and access to decently paid jobs. There are benefits to migration - Scots, travellers of the world since commerce began, know that - but there are costs, too.

Migration Watch has been following the debate on Scottish independence. In its comment on the Scottish Government's White Paper, it called the proposals on immigration "unsound for Scotland and unacceptable for the UK", claiming they would open not just a back door to the rest of the UK but a "barn door". One might disagree, but it would be foolish to assume the matter will not come up in any negotiations on independence.

Besides being the year of the referendum, 2014 is the year when Scotland welcomes the world to events ranging from the Commonwealth Games to the Ryder Cup. This is the "Year of Homecoming" in case you did not get the memo. While discussing migration might seem at odds with the prevailing mood of internationalism, it is a discussion that ought to happen.

There is a liberal bias on this issue. As a good liberal, and a former migrant to boot, it is a bias I will freely admit to having. But it must also be recognised that there are other views and they deserve a hearing. Ignoring concerns would be undemocratic, patronising, and unfair, not least to those who come here in search of a better life and find there is not enough of it to go around. Saying nothing is a cop-out, and it is one that the affluent classes, in many instances removed from the fray, are only too keen to take. Yet with a finite amount of cash available, a queue is a queue is a queue, whether it be for a council house or an operation. Unlike the festive decorations, those are realities that will not be disappearing any time soon.