Britons from Scotland are the butt of many jokes. They are, apparently, financially cautious, fond of liquor and mistrustful of fruit. They delight in sexualised invertebrate torment and underestimate in their provision for female public toilets. And they over-indulge in recreational drug abuse. In fact, one of the few insults witty enough to be forgivable is Samuel Johnson's playful 1755 dictionary definition of the drug ketamine as "A tranquilliser, which in England is generally given to horses, but in Scotland appears to support the people". But I don't think jokes such as this have spurred Scotland to sever England's apron strings.

Before I go any further, let me explain that, like all English broadsheet columnists, I absolutely love Scotland. I spent most of my 30s thinking I was Scottish, before realising I had misread my adoption papers. But would I have been Scottish had I been made of Scottish sperms but raised as English? Or is national identity the result of cultural conditioning? Wee Jimmy Krankie, winner of the Most Scottish Person in the World 2003, aside, who is Scottish anyway?

Curiously, as a teenager, I enjoyed all the Scottish indie bands – the Cateran, the Primevals, and del Amitri (first album only); in my 20s, I was inspired by quintessentially Scottish writers – Neil M Gunn, George MacKay Brown and Ossian the bard; cheap Scottish shortbread sustained me in the lean years of my 30s; and, more recently, it was that treacly Scottish heroin that finally freed my imagination to make me the important artist I am today. I even spent my honeymoon, admittedly in error, in Shetland in December 2006. And when I first crossed the border, to the Edinburgh fringe in 1987, I felt I was coming home.

Realising I wasn't Scottish left me bereft. I no longer had any genetic claims to the heathery Highlands or the literary high grounds. Alex Salmond's self-satisfaction with imminent Scottish independence is understandable, but he reminds me of the mayor of a small provincial town, who has got ideas above his station, because his brother in law has a cow that defecates ice-cream; the sort of cocky provincial mayor who then topples off a stepladder while unveiling a statue of the cow, which has made the town rich, and falls into a trough of its frozen anal produce. I would love to put the case for non-independence to Alex Salmond but I doubt he would speak to me again.

I first met Alex Salmond at a reception for young English playwrights at the new Scottish Parliament during the Edinburgh fringe festival in 2004. The event celebrated a scheme whereby we collaborated with Scottish translators to make our work saleable north of the border, a process that involved the painstaking insertion into our texts of thousands of swearwords, such as cunt and fuck. I attended the event with Mark Ravenhill, whose 1996 play, Shopping, had been retitled Shopping and Fucking for its hit 1997 Edinburgh run. This Scottish On Stage Swearing Initiative had led to the massive popularity with Edinburgh fringe theatre audiences of a newly sworn-up version of Richard Thomas's Jerry Springer: The Opera, to which I had helped contribute a further 6,000 new obscenities specifically for the Scottish market.

At the event, Alex Salmond and I were standing next to a buffet overflowing with Scottish produce, – venison, Baxters soup, Highland Toffee, shortbread, heroin and salmon. "I'm sorry," I said, "I didn't catch your name." "Alex Salmond," Alex Salmond said, but because we were standing near the salmon at the time, and because he had a Scottish accent, I assumed Alex Salmond had said: "I like salmon." So I said: "Yes. I like salmon too, but what is your name?" Again, he said: "Alex Salmond." And I said: "Yes. I like salmon too, as I said, I like all the Scottish foods. What did you say your name was?" After a further 15 minutes of this, and in a prophesy of future national relations, I Like Salmon walked quietly away with his financial backer, Brian Souter, the bus magnate accused of homophobia whose fleet of vehicles may yet ship undesirables south.

As someone who once thought he was Scottish, I understand more than anyone Scotland's anger at the English. Directives from Westminster seem more irrelevant to we Scots than ever, now that the cabinet is essentially an elitist cabal run by former members of the exclusive, window-smashing dining society, the Bullingdon Club. And none of them is Scottish either, apart from the bad-news patsy Danny Alexander and the eel-faced Trot fantasist and yacht fancier Michael Gove, who is adopted anyway, and could have ended up being raised anywhere in the UK, and so cannot make any especial claims for being anything but an orphan with a grudge.

But what the Scots must understand is that the Bullingdon Club cabinet has as little in common with the average English person as it does with the average Scot. If 5.5 million largely non-Conservative-voting Scots sever their links with us, there are 5.5 million fewer of us to say no to Bullingdon Club rule.

Mel Gibson's 1995 film Braveheart, while an admittedly appalling and historically inaccurate confection of gay-hating fascist propaganda, did inspire the desire for Scottish independence at grass roots. But the abysmal film is not without a certain nobility. Its closing reel takes place at the battle of Bannockburn, the garden of Eden of modern Scotland's Genesis myth. Robert the Bruce, who betrayed Braveheart at Falkirk and is now a puppet king loyal to the English, turns on his masters, liberating the Scottish people. At its simplest, this scene is about the Scots defeating the English. But it is also about doing the right thing, about a powerful figure going to the aid of those in need.

In turning his back on us, the English, in our hour of need against the common enemy of the Bullingdon Club government, Alex Salmon is not the Robert the Bruce of the battle of Bannockburn, noble and brave. He is the Robert the Bruce of the battle of Falkirk, a self-interested turncoat, piercing the heart of the everyman Wallace with the lance of his own vanity and pride and leaving the body, like the body politic of the nation of England, to be castrated by David Cameron and have its once erect British penis flung into the air to be snatched by pigeons and ducks. In short, Salmon is something no son of Wallace would ever want to be. A coward, fleeing the good fight, and leaving those who fight on to suffer their fates alone. I never thought I'd say it. But today Alex Salmon makes me glad I am not Scottish after all.