Passions are running high. The referendum on Scottish independence is less than a month away; at this point it is hard to think of an argument that hasn’t been hashed, rehashed and hash-tagged. Few of them will make a blind bit of difference to the outcome.

Yes, the independence debate is about economics, currency and financial stability. There are topics on which it is (at times) possible to have a rational discussion. But it is also about identity, patriotism of different stripes and a sense of belonging. And these are things that more or less defy balanced deliberation. Who is to say which, ultimately, is the more important? Should you vote with your head or your heart? That’s up to individuals to decide.

It is when high passion and economic argument mix that things become particularly worrying. As we report in The Daily Telegraph today, Sir James Mirrlees, one of the Scottish government’s main economic advisers, is suggesting a newly independent Scotland should welch on its portion of the UK national debt if it is denied access to a sterling currency union.

This is incendiary stuff; you don’t have to be an ultra-unionist to see why this kind of talk might spook the markets. Nor is it scaremongering to suggest that business and financial leaders are far from enamoured with the uncertainty that the Scottish independence vote has created.

Almost the only thing that we know about the outcome of the referendum is that it will change Scotland’s relationship with the rest of the UK. And that holds even if there’s a No vote.

On the other hand, the list of things that we don’t know is seemingly endless. Would Scotland be able to make a success of life as an independent nation? Of course it would. But that doesn’t rule out the possibility of significant hiccups in getting from here to there, nor that it would lose something in the process.

David Fuller's view

My guess is that the polls on Scotland’s vote could easily tighten before the referendum vote on 18^th September.

If so, the uncertainty will be a headwind for the UK stock market.  Currently, the FTSE 100 Index is near the upper side of a 16-month and counting trading range. Demand marginally holds the upper hand, evidenced by the gradually rising lows, as one would expect given the BoE’s accommodative monetary policy.  A close beneath 6500 would temporarily erode recent support and be a technical warning unless immediately reversed.