Michael Moore, the Scottish Secretary, could be forgiven for kicking his Scotland Office desk after the expert in question, Professor James Crawford of Cam-bridge University, lauded as the authority on international law by Whitehall insiders, was asked, in the event of Scottish independence, about the SNP Government's ambitious transition timetable and the prospect of an independent Scotland having to apply to international organisations for membership.
The view from London SW1 is Alex Salmond's 18-month timetable is "fanciful" and the prospect of applying to bodies like the EU, with 27 members, will hardly be "a piece of cake".
Yet the good professor suggested the 18-month timetable was, in fact, "realistic" and applying to a range of international bodies would not be difficult "in most cases".
Nicola Sturgeon, appearing on the radio alongside Mr Crawford could barely believe her luck when the eminent academic backed up her political line instead of Mr Moore's.
With a deal of understatement, she declared Mr Crawford's contribution had been "helpful" and the UK Government had been guilty of a "huge own goal". Perhaps Mr Moore will ask for his money back.
In contrast, the First Minister's Fiscal Commission concluded an independent Scotland would be better off with sterling and it would, by the way, also be good for the UK; which just happens to fall in line with Mr Salmond's own thinking on the subject.
However, their assertions about an Independent Scotland sharing management of a sterling zone with a key role in the Bank of England might have Chancellor George Osborne choking on his beef lasagne and suggesting the FM is being a mite presumptuous given Scotland, post-independence, would actually be a foreign country.
The commission says there would have to be extensive negotiations with Whitehall, underlining again how the once smooth highway to independence envisaged by the Nationalists is now looking full of difficult twists and turns.