So there I am talking to Jim Sillars about independence, and a second referendum, and how well, or badly, the Scottish Government is doing, and we end up talking about Liverpool FC, and EastEnders, and Only Fools and Horses, and Jerusalem which, believe it or not, is Mr Sillars’s favourite piece of music. “I will not cease till we have built Jerusalem in England’s green and pleasant land.” Imagine for a minute a former deputy leader of the SNP heartily singing along to that one. Quite an image isn’t it?

But, in a way, what Mr Sillars had to say about his cultural preferences really matters because it touches on one of the factors that undoubtedly had an effect on the result of the 2014 referendum and will probably have an effect on any future one but is rarely talked about. Mr Sillars called it the “sphere of influence” but, whatever you call it, it’s a form of union between England and Scotland that’s enduring and unlikely ever to disappear. Perhaps Scottish nationalists could even learn to love it because they must certainly learn to live with it.

One of the first people to describe the phenomenon, according to Mr Sillars, was his late wife, the nationalist MP and MSP Margot MacDonald. “Margot was the first one to mention and describe it,” he told me. “The unavoidable social union after 300 years. You laugh at the same television programmes. Do you think people would stop watching EastEnders if we were independent? No. Would my eldest grandson and I cease our interest in Liverpool FC, which I’ve followed all the days in my life? We fought in the wars together, which is not unimportant. I once joked with Margot 'if we’re independent, you leave the Royal Navy alone'. I have a love hate/relationship with it, but I have an enormous affection for it.”

The critical question, of course, is what effect the social union has, and will have, on our lives and our politics and Mr Sillars had several things to say about that, some of which I agree with, some of which I don’t. He told me, for example, about a conversation he’d had with Ian Blackford about the right strategy to win independence. Mr Blackford, as we know, likes to rattle sabers and bang drums and blow whistles but Mr Sillars told him there was far too much in the SNP about “evil Westminster” and “power grabs” and that a much more subtle strategy was required, one that acknowledged the sphere of influence and the social union. It’s a union that means many of us are actually pretty well disposed towards England and all things English, and for personal and political reasons, we should protect and nurture that relationship as much as we can.

Mr Sillars described it this way. “Whether we like it or not,” he said, “as Scots, we have been in England’s sphere of influence for centuries and it’s unavoidable. We live on a single island. We live together and we’ll always live together and our statesmanship should be based on the reality – we’re a small part in that relationship and we want to have the best relations possible. It doesn’t mean we’ll always agree with our colleagues south of the border. But the prime purpose of Scottish foreign policy must be to have good relations with people in England. It’s as simple as that.”

As a riposte to the teeth-bared school of nationalism practised by Ian Blackford, I totally understand where Mr Sillars is coming from. Apart from anything else, if Scotland ever does go independent, the English side is unlikely to feel well disposed towards us in the negotiations after years and years of the Blackford technique. Mr Sillars also had some interesting things to say about the kind of relationship he and Margot had with unionists. The last non-family member to see Margot alive was her friend Fiona who was not a Yes voter but was a bosom pal. Margot also talked to Jim about the divisions she feared that the 2014 referendum would create, and in the end did create. The point is: we’re all in the same sphere of influence, the same social union, so let’s all try to be nice to each other.

The other important issue – and maybe the most important one in the next few years – is to what extent the social union affects our views on independence and therefore the chances of the nationalists ever winning a referendum, and Mr Sillars’s opinion was pretty clear. There is no reason, he said, why Scots cannot want both to be independent and also love the social union. As he said: do you think people would stop watching EastEnders if we were independent? It’s a fair question and the answer is no.

But I wonder if Mr Sillars, and others in his party, are under-estimating the ultimate power of the social union. It’s commonly thought that it was the economy that lost it for Yes – people were worried about the currency, and their jobs, and their pensions – and of course that was a critical factor. But I’ve spoken to many No voters for whom much softer factors, linked to the social union, were also important. And there’s no reason to suppose they won't continue to be important.

In Mr Sillars’s case, it’s Liverpool FC and Jerusalem, but in my case it’s How Soon is Now? and Acorn Antiques and The Horror of Fang Rock and it’s Alnmouth and London and it’s many other things that are English but are also mine. I guess nationalists would say all of these things would still be there in the event of independence – that would certainly be Mr Sillars’s argument. But the point is they are more than mine: they are part of me and my identity, and so are the songs not yet written or the shows not yet made or the buildings not yet built. Put it this way: I remember saying to someone before the 2014 referendum “I do not want to lose Big Ben” and, seven years on, that’s still the way I feel.

Naturally, there will be some in the independence movement who will mock or dismiss such concerns, possibly because they do not understand them or, in their heads and hearts, they prioritise Scottish culture. But if the SNP is ever to win a referendum, it must become much more subtle in its understanding of how many Scots feel about England and just how strong the social union is.

Partly, such a new, more subtle strategy would be about turning down the dial on the likes of Ian Blackford – for all our sakes. But it’s also about seeking a much more intelligent and mature attitude towards the cultural and social bonds that underline the political ones. Think of the English who loves Burns. And the Scots who love Shakespeare. Think of Liverpool FC and EastEnders. Think of a former deputy leader of the SNP singing along to Jerusalem.

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