This week Finance Secretary John Swinney will publish his forecasts for the oil revenue which could accrue to an independent Scotland after 2016 ...

and they are likely to be markedly more generous than those from the UK's Office of Budget Responsibility. Unionists will no doubt sigh that, behind in the polls, the SNP has broken the emergency glass and revived its old slogan: 'It's Scotland's Oil'. They will point out that oil prices are volatile, that their zigzags make budgeting difficult.

But the SNP should be talking about oil. It is the gut issue of the referendum debate. Billions upon billions of pounds are at stake.

Loading article content

Unionists talk as if all this money is a handicap, a volatile menace to society. But with the referendum ahead, there has never been a better time to consider just what Scotland gets in return for its oil, and whether, after 40 years of allowing it to bypass the citizenry en route to the Treasury, we should simply continue to wave it on its way.

It is not hard to see why the Unionist side is so keen to silence the argument over oil. The SNP's job now is to say how it would use it.

Swinney's intervention comes after a week in which the Better Together campaign managed to successfully torpedo a highlight of the SNP year – the Gers figures showing Scotland was £4.4bn relatively better off than the UK in 2011-12 given its fair share of North Sea oil.

Better Together eclipsed this by gift-wrapping a leaked Cabinet paper for the press.

Written by Swinney last summer, it set out some of the cold financial facts an independent Scotland would face. That the leak received more prominent coverage than Gers was taken by some Nationalists as proof of an inherent pro-Union bias in the media.

In reality, the first Cabinet paper to be leaked under the SNP was simply too good a story to resist.

Better Together was only doing its job. Swinney's intervention today suggests that those in favour of independence have realised the need to seize back the initiative.

If the finance secretary can join the dots with the same honesty and clarity seen in the leaked paper, Better Together's good week may be its last for some time.