Treasury shot Danny Alexander in the foot

Even before its publication, Professor Patrick Dunleavy, a political scientist and public policy expert at the London School of Economics, had comprehensively trashed a claim in the report (based, in a highly cavalier fashion, as it turned out, on his work) that the start-up costs of an independent Scotland could be as high as £2.7 billion. The Treasury's approach was "crude," he said. Its report "woefully misapplied" his own research on the costs of creating new government departments. He later guesstimated (his word) the real costs an independent Scotland would face at between £150 million and £300m in various press interviews, a fraction even of the Treasury's more cautious 'official' estimate of £1.5bn.

The UK Government's gaffe was a gift to Alex Salmond. Launching the Scottish Government's rival economic report a few minutes before Mr Alexander got to his feet on Wednesday, the First Minister devoted much of his time to denouncing the Treasury. "Mr Alexander's figures are in meltdown, and the Treasury have been left without a single shred of credibility," he said.

The Treasury's slapdash efforts have exasperated those in the No campaign who feel under no obligation to defend the Coalition Government. "Why did no-one phone Dunleavy?" asked one Holyrood politico with a weary shake of the head, shortly before the professor himself, as if to rub it in, blogged: "If officials had rung me at any time (as e.g. any good journalist would) I'd have been very happy to brief them on our findings."

Their second gripe was over the UK Government's habit of trailing parts of their regular Scotland Analysis reports days in advance. Not only does it give the Scottish Government plenty of time to rebut the findings, it ensures media interest is on the wane by the time the document comes out, critics complained.

In the latest case, briefings on the contents of Wednesday's Treasury paper began the previous Friday.

In the end the blunder almost, but not quite, overshadowed the whole point of the rival reports - the UK Government's claim Scots were £1400 better off as part of the UK on the one hand, and the Scottish Government's claim they would be £1000 to the good after 15 years of independence on the other.

If you missed at the time, here's an action replay of the Treasury's own goal. What officials did was to take Professor Dunleavy's estimate of £15m for the cost of setting up a Whitehall department and multiplied it by the 180. That figure was derived from the SNP's independence White Paper which talks about replacing some of the 300 UK public bodies operating in Scotland. Nowhere, though, does it suggest an independent Scotland would require 180 new bodies each the size and scale of a big government department. The very idea flies in the face of common sense.

Of course if £2.7bn or even £1.5bn are the wrong answers to the question: "How much would it cost to set up the bodies required to run an independent Scotland?" it seems fair enough to ask for the correct figure.

Plucking a number from Professor Dunleavy's guesstimated range, Mr Salmond declared £250m a "reasonable" sum. However, it later emerged the Scottish Government had no calculations to support the claim - and nor will it. The actual cost could only be known following post-Yes negotiations to divide up the UK's shared assets, the First Minister's chief political spokesman said.

As man of the moment, the last word should go to Professor Dunleavy, not least because he neatly summed up the story in his blog. "I think," he wrote, "that UK ministers and the Treasury potentially have a point in arguing that the Scottish Government has not been very forthcoming, they might even say evasive, about clarifying some of the costs entailed in independence. But there is no point in putting into public circulation misinformation to try to counteract that."