A reader sent us an interesting snippet of information today.

That seemed a startling fact, so we looked into it. And it’s true.

“RTS” is the UK government’s – or more precisely HMRC’s – Regional Trade Statistics accounts, which seek to disaggregate the UK economy to see how much money is generated in which areas. When independence supporters first discovered that the large bulk of North Sea oil revenues were attributed in the stats to an “unknown region” rather than to Scotland – Wings readers knew about it at least as early as July 2014 – Unionists went into overdrive to downplay and obfuscate the fact.

But as of this year, with the independence referendum safely long in the past, the UK government has very quietly altered the methodology of RTS to now accurately credit oil revenues to where they belong.

If you look at the figures published in 2016, they put Scottish production of “Mineral Fuels” at £1.76bn for 2014 and £588m for 2015.

But the latest figures backdate those numbers up to £10.6bn and £6.8bn respectively.

In just two years, then, Scotland’s economy has suddenly produced over £15bn more than the official UK government figures had previously claimed it did. It’s a bit like popping out to your garage to fetch a screwdriver and discovering a Ferrari you didn’t know you had under a dust sheet.

Now, we’re not remotely expert enough when it comes to the labyrinth of government trade stats to determine how significant that is (the £15bn, not the surprise Ferrari). But we suspect readers will agree that it seems an awfully big statistic to alter without mentioning it, or having anyone notice.

And if there was nothing shady going on before, why change the rules now?