There is one clear message from today's thoughtful speech by Mark Carney the Governor of the Bank of England - that the failings of the Eurozone show that to have a successful monetary union you require fiscal and political union. This is a detailed speech but make no mistake, the Governor's judgement on currency unions is devastating for Alex Salmond's currency plans.
Currency is fundamental to the nationalists' economic case for breaking up the UK, insofar as one even exists. Whether it's pensions, renewable subsidies, mortgage rates or savings, Alex Salmond's plans hinge on Scotland and the rest of the UK entering into a binding agreement to veto one another's budget, tax rates and borrowing levels. If a currency union isn't possible the rest of the SNP's already threadbare economic case collapses like a house of cards. It would appear that the idea of a currency union is now off the table. Alex Salmond can only bury his head in the sand for so long before he has to tell the people of Scotland what his Plan B on currency is. Would we join the Euro? Or would we set up our own currency?
The choice we face is clear - believe Alex Salmond or believe the experts and the facts. As part of the UK, we are better placed to tackle the long term challenge of sustainable public finances. Things are difficult just now, but the IFS report makes clear that they would get much worse if we separated from the UK. That is a risk that we really don't need to take. Coming little more than a week before the publication of the SNP's crucial White Paper, the IFS report poses a significant challenge for Alex Salmond. The White Paper must face up to the consequences of independence, including the need for big spending cuts and tax rises. If it doesn't, then it won't be worth the paper it is written on.
There was a historic shift in the independence debate this week - but you might not have noticed it. The row of the last few days has focused on the gap between what the SNP Government says in public about the affordability of an oil fund and what their economic advisers told them in private. As important as the issues of trust raised by this affair were, the really significant consequence of this week's debate is the SNP's admission that all oil taxes are used to fund current spending.
Oil has always been central to the nationalist case for independence. It has been used by the SNP to make all sorts of expensive promises about what would happen after independence. The inconvenient truth which the SNP have always struggled to deal with is that all the revenues from the North Sea currently go towards spending on public services, pensions and benefits in Scotland.
It is increasingly clear that Alex Salmond will say and do anything to get us to vote for independence. For months we have heard him say that there is £1.5trillion worth of reserves remaining in the North Sea. Yet this week it emerged that this is based on dodgy figures which show a fundamental misunderstanding of the sector. This is a blatant attempt to cook the books in order to fool the Scottish people.
As public and parliamentary support for HS2 falls, surely it is only a matter of time before one of the parties changes their position. At the rate things are going, the debate may well descend into a race to see who will be the one to push the plans well and truly off the rails.
Salmond thinks that suggesting a debt free start is good politics, but people understand there are consequences. If you declare yourself bankrupt you don't start anew with a fresh slate, your bad credit history follows you around for the rest of your life. The consequences for borrowing, business and mortgages would be dire.
A couple of months ago, while promoting his new book, former Chancellor of the Exchequer, Alistair Darling, let slip to the BBC that during the 2008 crisis he had become so exasperated with the Governor of the Bank of England, Mervyn King, that he sought advice from the Treasury on whether he could over-rule the Bank.
"How were we so blind?", Britain asks itself, "the signs must have been there all along", before remembering that, "they seemed so happy together." Well, Britain, I got news for you. Gordon Brown and Alistair Darling aren't the first 'happy' couple to have found themselves at one another's throats.
Poor Mr. Brown. Our former Prime Minister is subject to another onslaught from someone who used to work with him, and who is now, it appears, prepared to tell it like it was. Who cannot help but sympathise?