ON Tuesday, Nicola Sturgeon told the Scottish Parliament that after a year of negotiations, agreement in principle had been reached on the fiscal framework that will underpin the additional powers for Scotland set out in the Smith Agreement.

It is an extraordinary achievement by the First Minister and her inestimable Finance Secretary John Swinney. As the Daily Record noted the following morning, they are the first political partnership in the history of British politics to take on the Treasury and win.

There are some very important reasons why this matters and some very important reasons why we shouldn’t fall for the Unionist spin that it is “job done” and promises honoured, far less that we should all be very grateful and quietly go away.

First, why it matters.

During the referendum campaign, we all became very familiar with the Barnett formula, the mechanism the UK Government uses to decide how much money Scottish Government is to be “given” through “the block grant”. It is based on an assumption that all tax powers would rest at Westminster, so with some of those powers coming north and with the commitment to continue to use Barnett to determine the size of the block grant, a means of taking the tax revenues raised by the Scottish Government into account has to be arrived at. They call that the “Block Grant Adjustment”. The size of that adjustment needs to be determined each year and the way of reaching that is a critical part of the fiscal framework.

A key principle of this, agreed by the Smith Commission, was the principle of ‘“no detriment” that neither the Scottish nor the UK governments should suffer financially just because tax powers have been transferred from Westminster to Edinburgh. So, the basis of calculating this adjustment formula is critical.

The upshot of all of this is that it is not only about the actual powers that come to Scotland, it is also about the integrity and fairness of the fiscal framework on offer. The two go hand in hand. Get it wrong and it’s like being offered the chance to earn more money by doing extra hours, only to have the additional money you’ve earned deducted from your basic wage.

As we know, there’s many a way to calculate a formula and in this instance, it is not about small sums. Leading economists such as Professor Anton Muscatelli highlighted how some formulas can penalise us and others can produce a fairer result. The key question is what happens if the Scottish population grows more slowly than elsewhere in the UK and the Scottish Government, holding fast to the “no detriment” principle argued that the formula should take that into account. Why? Because lower population growth, which is not factored in, would lead to systematic reductions in the Scottish funding levels from Westminster.

So, adjusting the formula solely on the basis of income tax powers, without factoring in population growth variations, is a straightforward route to a great deal of “detriment” for Scotland. Initially, in the minds of the UK Government, £7 billion worth of detriment.

Of course, the Treasury was at it. It wanted to reduce the money coming to Scotland by as much as possible and saw the fiscal framework as an easy opportunity. But it reckoned without Mr Swinney and Ms Sturgeon. A pair made formidable by the fact that their stance was based on some important principles. That the block grant to Scotland isn’t some generous gift from Westminster to the lieges in the north, but a proportion of our own money, earned in Scotland coming back to us, that agreements should be honoured and “no detriment” means precisely that, that their first priority is to stand up for Scotland. This was never Westminster setting out honourably to do the decent thing. A £7bn loss to Scotland wasn’t swallowed by our Government, so the next sleight of hand was to reduce £3bn by “giving” us a £4bn “present”. This was Tory Westminster chancing its arm and seeing how much it could get away with. These guys could give a stallholder selling a dodgy tea-set a run for his money. But their tricks were resisted and as Grahame Smith of the STUC said, anything other than a full “no detriment” deal would “incrementally eat away at the Scottish budget and cause serious damage within a decade”.

So agreement on the fiscal framework mattered not only because we now have one that honours the Smith Agreement but critically, because it was a win for principle over attempts at sleight of hand. Scotland is stronger today as a result.

But, let’s not get carried away. Our Scottish Government has won us all a good deal, but it is not “job done”. Because the big question running through all of this is why Scotland’s population growth is likely to be slower than elsewhere in these islands. And that takes us right back to central argument over economic powers. So while we can now look forward to using the additional powers in Scotland to secure a fairer system of taxation and a socially progressive system of welfare support, we can’t take our eye of the ball.

The Tories and their Unionist chums in Labour haven’t wasted a minute in telling us to shut up and get on with it now. Yet again, from the creation of the Scottish Parliament in 1997, through to Calman, through to Smith, they insist on hoping that each step will see the end of calls for full independence.

What they are not hearing above the sound of their own voices is the growing clamour for independence, strengthened and sustained by the SNP Government’s capacity, year on year, to demonstrate that Scotland can use whatever powers we have wisely and to good effect and all the time, demonstrating what Scotland could do if we were independent.