I broadly agree with this. It also doesn’t particularly matter for the purpose of this debate whether the SNP are “right” from an economic perspective – the fact that there is a perception the currency union wouldn’t be in the rest of the UK’s interest is enough to guarantee it won’t happen. Politically it would also be an extremely hard sell – e.g. the UKIP lobby is hardly going to rush to back the idea.

I do think the implications of the argument are pretty dreadful from Salmond’s perspective. It doesn’t seem credible to continue to argue for seven months that the rest of the UK (and Nicholas MacPherson) are simply lying for the sake of the referendum campaign. Yet Salmond’s own speech did a pretty good job of summing up exactly why independence without a currency union would create problems for the Scottish economy. About all he’s left with is grandstanding about bullying and scaremongering.

I personally feel that the big ticket item and the first item in MacPherson’s letter is the fact the Currency Union is only viewed a “Temporary” by Scotland.