scotland debate
Alex Salmond and Alistair Darling take part in a live television debate hosted by Bernard PonsonbyGetty

You know that really important appointment you've got tomorrow morning? How do you plan to get there on time? Ah, by train. But what if the trains are running late? Oh, I see, you'll aim for an earlier train to be on the safe side. But what if the trains aren't running at all? All right, fair point, that doesn't happen very often, but it does happen now and again, and you simply can't afford to miss that appointment.

What's that you're saying? If needs be, you could get there by bus or taxi, or you could get a lift from a friend? Well, that's no good, is it, because you've just listed three options – you still haven't told me how you plan to get there on time. Eh? What do you mean, "by train"?

In the real world, the purpose of having a "Plan B" is simply the reassurance of knowing that you have at least one workable alternative course of action if something goes awry. If you've got more than one alternative, so much the better. You don't need to decide in advance whether you would take the bus or a taxi, or ask for a lift – in fact you've got an embarrassment of riches as far as Plan Bs are concerned. You can feel free to start your day with confidence and without catastrophising, because in all likelihood the trains will run, and, whisper it gently, they'll probably run on time.

If there was any credibility to Alistair Darling's claim in Tuesday night's TV debate that he was only tediously demanding a currency Plan B on behalf of Scotland's poor fretting electorate, he would have saved his breath. As Alex Salmond reminded him repeatedly, the Scottish Government's Fiscal Commission set out a range of Plan Bs months ago, so an independent Scotland will have several alternative options available in the fantastically improbable event that the London government cuts off its nose to spite its face, and refuses to enter into a formal currency union.

We could establish a nominally independent Scottish currency, pegged to sterling. We could join the euro. Or we could continue to use the pound outside a formal currency union, as Darling conceded was perfectly possible, without London's permission.

So Scotland can go about its business in the referendum campaign with confidence and without catastrophising. We know that the London government will almost certainly agree to a currency union, because a senior UK government minister admitted as much privately to the Guardian, and indeed because Darling himself said only last year that such an outcome would be "logical and desirable". But even if they don't, the contingency options are there in abundance. So why, you might wonder, did Darling treat the people of Scotland with such utter contempt by wasting a huge chunk of the debate on an issue that has been long since resolved, rather than using the time to set out his vision for why Scotland should not govern itself?

The answer, of course, is that to the extent such a vision even exists, it is deeply unattractive to the electorate. Every minute that Darling spends pointlessly chasing his tail on subjects like the currency is seen as a small victory, because it's one more minute during which he has successfully avoided making the case for Westminster rule. And it's no exaggeration to say that this entire "Plan B" idiocy is a strategy concocted specifically to enable Darling to chase his tail as much as humanly possible.

It's been privately admitted that George Osborne had no intention of ruling out a currency union (because he knew he'd have to do an embarrassing U-turn in the event of a Yes vote) until Darling insisted. The idea was that Salmond would be forced into specifying just one Plan B, rather than pointing to a range of options – and then Darling could demand yet more moronic specificity. "What do you mean you haven't yet decided whether a Scottish pound coin would be hexagonal or circular? The people of Scotland demand answers! Their savings are at risk!"

With his customary shrewdness, Salmond avoided stepping into that trap. On Tuesday night, he turned the tables on Darling by exposing the absurd double standard in the No campaign's approach – they demand absolute certainty on every dot and comma of how an independent Scotland would work, and claim that without it the Scottish electorate cannot possibly be invited in good conscience to vote Yes. And yet at the same time they shamelessly invite people to vote No without providing even a shred of certainty on a range of key issues.

Can we be sure that Scotland will still be in the EU after David Cameron's in/out referendum? "No, but I'll campaign with you to stay in!" Well, that's a relief, Alistair – after all, who cares about whether we're in the EU as long as we have the comfort of you being on the losing side along with us? And what new powers will be given to the Scottish Parliament in the event of a No vote? "Some! And you'll love them!" Fair dos – who needs detail?

You probably won't have heard much from the London media about those parts of the debate when Darling was on the ropes. That's because, by and large, the London media are cheerleaders for the chase-your-tail distraction strategy, and they practically wet themselves with excitement that STV's format allowed Darling to chase his tail for such a prolonged period. But I've lost count of the number of people who have shaken their heads in bewilderment and said that the debate they watched on Tuesday bore no relation to the "Darling win" they read about later in certain papers, and heard about in certain news programmes.

The only hard evidence that the media and the No campaign have been able to point to is a single poll conducted after the debate by ICM, and which the leading polling expert, Professor John Curtice, pointed out was of limited statistical reliability because certain groups of respondents had to be upweighted by an extreme amount. But for what it's worth, even that poll showed that undecided voters thought that Salmond had won the debate.

It's even worse than that for the No campaign, though, because in a sense Salmond was in a no-lose position on Tuesday. All the evidence suggests that well-informed voters are tending to vote Yes, whereas No voters are more likely to be people who have until now shut down all thought on the issue of independence, perhaps because they find it tiresome. Anything that raises the profile of the issue helps the Yes campaign, because it encourages people to think and to seek out information. And if they find to their frustration that they can't get that information from a TV debate because Darling sabotages it with a wall of meaningless "Plan B" noise, they'll just be even more motivated to find it elsewhere – on the internet, or from talking to friends, or by going to a public meeting.

Splendid work, Alistair. More please.

James Kelly is author of the Scottish pro-independence blog, SCOT goes POP! Voted one of the UK's top political bloggers, you can hear more from James on Twitter:@JamesKelly.