Special deals: so many are being talked of as to make Theresa May’s maxim, ‘Brexit means Brexit’, look like a lot of nonsense. We can presume she originally had in mind that, whatever the substance of the eventual agreement as the UK takes leave of the EU, the form of it should remain simple and clear with no fudging of the central principle. The Brits will go and shut the door firmly behind them, even if they feel no need to slam it.

In the real world such simplicity and clarity are hard to find. Partnerships of 40 years’ standing will always be difficult to dissolve, even with goodwill on both sides (which is not to be counted on here). Quite apart from the official treaties and other documents seeking to put the relationship on paper, the UK and Europe have forged invisible bonds. From the obliging Polish plumber who is always on call to the students who go and study abroad on the Erasmus programme, a thousand little European details make British life better.

As people have started to think about what they are going to miss post-Brexit, there has been a tendency for the government to turn from ‘Brexit means Brexit’ to ‘Brexit might mean a number of things’. This is the reason for the obvious disagreements inside Whitehall, even though the different factions are trying hard (well, not too hard) to avoid talking out loud about what is going on behind the scenes. There are men and women of stern and unbending principle at work here: always a dangerous thing in politics. There are others that just want a deal they can sell, to their colleagues, to their party, to the public at large. Liam Fox is an example of the hard men, Philip Hammond of the softies. Theresa May? If only we knew.

This week the biggest stooshy arose from the leak that the government is seeking some way to preserve the enormous amount of business that the City of London does in the rest of the EU. Without that business the income and wealth of the Tory heartland in the south-east of England might vanish like snow off a dyke, and Brexit would have turned out to be a disaster even from May’s point of view.

It is true that in the EU, despite our 40 years of membership, we are still a good way from free trade in financial services – though it remains an aspiration, and that limited degree of freedom of trade which has been achieved can by the rules never be taken away again. What we have got instead is the so-called passporting arrangement which allows, short of a full system of common regulation, for the traders licensed in one member country to operate in all the others. This applies in the whole UK as well, and Scottish financial outfits, the biggest of which is Standard Life, benefit too. It is a sectoral rather than a geographical matter, and so it would stay under the new deal the UK government is reported to be seeking.

There is no problem seeing why a full-frontal Brexit would be undesirable in this instance, despite the surge of testosterone likely to be generated in Fox. Hammond knows the dangers if the City of London is knocked off its financial perch. Its rivals in Europe, Frankfurt or Paris, Amsterdam or Milan, are all smaller, weaker and less successful. They look jealously on the freedom from regulation of the British industry. Not that there is any prospect of their now gaining the same freedom from their own governments, which are all far too nervous of international capital markets to allow it. And in fact many of these foreign financiers are not that keen on it either, since it would introduce a great deal more alarming risk to their own businesses. But it would certainly make their personal lives easier, with extra time for lunch and golf, if the City of London were cut down to size.

Still, when it comes to monetary skullduggery these people are no slouches either, and I understand from Brussels that they have hatched a plot of their own. Whenever the Brexit negotiations finally get underway, the UK will be offered a financial deal that classifies it as a so-called third party in its dealings with the EU. This would oblige the UK to maintain a regulatory environment at least equivalent to the one inside the EU if it is to continue doing business there. In other words, there would be not more freedom but less freedom for British finance – which is not the idea of Brexit at all. We can well understand why the UK government is anxious to get in its own bid for this particular game, even at the risk of appearing more anxious to protect the interests of the fat cats in the City than of anybody else.

Where does all this leave Scotland? The City’s deal from Brexit will be important to us too since finance is such a vital part of our own economy, on which thousands of jobs depend. But the whole guddle is muddied by the Scottish Government’s intention to stay inside the European single market. And in fact bright sparks in the SNP have already demanded that if the UK government wants some such arrangement for the City of London, then there can be no logical objection to seeking it for Scotland as well. I’m not sure this idea really works; one is a sectoral, the other a geographical matter. But there is no harm in punting it anyway.

The concept of Scotland outside the EU yet inside the single market is certainly in need of more convincing arguments. I can see the political appeal and the value of it as an expression of the will of the Scottish people in the European referendum. But the practical obstacles are enormous. Without going further into detail, let’s just take a couple of the four freedoms that the single market embodies, for goods and services, capital and labour.

In the case of bad blood after Brexit between the UK and EU leading to possible sanctions on trade in goods, then there would need to be border controls at Berwick and Carlisle. The same in any event is true in the vexed question of immigration, which for Theresa May and many other English people seems to have been the main motive for getting out of Europe – whereas in Scotland we want and need immigrants for our own economic purposes and the Scottish Government officially welcomes them. In the single market EU citizens are able to move and work where they like which means, if Scotland stayed in the single market, they could continue to come here. If some then wanted to move on into England, it would be up to the English to stop them, again with border controls at Berwick and Carlisle: and this all in one UK!

In short, the concept of a Scotland with a special deal outside the EU but inside the single market seems to me wishful thinking. It is rather typical of many fond hopes likely to be shattered. More and more, I can see a hard Brexit coming, though personally I dislike the prospect. Donald Tusk, the Polish president of the European Council, who since his youth as a student leader of Solidarity has seen his country go through a lot of tough times, said the other day the UK could have ‘hard Brexit or no Brexit’.

I suspect he is right, and even more right in the case of Scotland.