THIS week Boris Johnson did us all a service.

Now that is not a sentence that has ever opened a column in The National before. Nor is it likely to again until he signs the Scottish Independence Agreement as the UK prime minister in the not too distant future.

But the pre-launch for his leadership bid headlined on what the Scottish media dubbed a new “Tory Tartan Tax”. He wants to cut the amount of income taxed at the top rate pretty dramatically. This will hand nearly £10 billion over to the richest earners. He will fund this by some as yet ill-defined combination of borrowing, spending cuts or increases in national insurance.

Deploying the best Trumpian communications strategy, it has been pretty much impossible to make head nor tail of what he actually is proposing in any true detail. His people spent the days after the announcement ducking and diving and obfuscating.

Many other Conservatives recoiled at this policy and the disorderly manner of its communication. Michael Gove said: “One thing I will never do as prime minister is to use our tax and benefits system to give the already wealthy another tax cut”. Dominic Rabb claimed it was “protecting privilege”. Rory Stewart, a “cheap electoral bribe”.

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Scottish Conservatives were more muted. We can guess why. But plenty were willing to be quoted anonymously condemning it.

Odd then that all three of these gentlemen fully supported the decisions of the last Conservative Budget in November 2018.

In that Budget, the Chancellor Philip Hammond did precisely what Boris Johnson proposes albeit on a much smaller scale. By increasing the top rate threshold to £50k he effectively ensured one million fewer people pay the top rate compared to three years ago. At the same time revenues from national insurance are set to be some £23bn higher in three years than they are now.

Not only did Johnson’s party critics back that policy then, they went on to attack the Scottish Finance Secretary Derek Mackay MSP for deciding that prioritising tax cuts for the better off was not the most important thing.

Well, if you are looking for consistency and candour in the politics of the Conservative leadership contest you will require an electron microscope.

Leaving aside the political knockabout for a moment though, why do I think the Johnson intervention did us a service? Chiefly because it highlights the wholly inadequate financial responsibilities of the Scottish Parliament.

The way devolution works now is designed to give the impression of financial responsibility while at the same time allowing the Treasury to continue to constrain it practically, economically and politically.

The vast number of taxes remain reserved to Westminster. The borrowing powers are completely marginal at just over 1% of the Scottish budget and this is really very important.

Income tax is devolved but only on income earned not returns on investments and not the crucial basic allowance. Some of VAT revenues are “assigned” but the formula for working that out is so arcane to be rendered nearly pointless in policy incentive terms.

Air Passenger Duty was devolved, but in the absence of other potential balancing revenue items to complete a rounded budget is extremely difficult to change as the potential broader impacts will not flow to the Scottish budget. And that is before environmental implications are considered. National insurance, corporation tax, energy, travel and numerous other taxes and duties remain reserved.

In many respects the most difficult tax for the devolved administrations to alter is income tax. Not only is it politically charged but with the labour market integration of the UK it requires very careful stewardship to protect revenues and unintended consequences.

You only have to watch the foaming fury of critics at the most marginal decisions taken not to just blithely follow whatever the Tory chancellor has done.

Devolution was supposed to be about equipping Scotland with the ability to pursue its own choices and approach, to take responsibility and to set its own course. However, the financial underpin has not followed suit. It encourages short-term fixes not long-term reform. Risk bearing and investment is extremely difficult.

Boris Johnson’s proposals highlight that in spades. Scottish national insurance contributions will be increased by the UK chancellor, while income tax payers will only receive a balance if the Scottish Parliament decides to emulate a policy roundly and rightly derided by all sides outside the Johnson inner sanctum. And this is always the case.

The Block Grant Adjustment mechanism does insulate the income tax revenues of Scotland from such divergences, serving to further emphasise that financial devolution is complex, constrained and completely inadequate.

The Scottish budget awaits the UK budget and determination on taxation and the block grant before it can consider what to do in the weeks it then has to legislate.

Too much, far too much, of the agenda is about mitigating policies from London we disagree with rather than longer-term strategies for what we want for our own economy and society.

Free tuition fees is a great example of a policy choice taken because devolution allowed it. However, the funding of that decision is hampered by whatever choice is made at a UK level about its own ever-changing policy on tuition.

The Barnett Formula emphatically does not ensure “largesse”, in fact it is designed to do the opposite. It is designed over time to ensure a convergence in spend per head in devolved budget areas with the UK average. This never made much sense and certainly does not post devolution.

It offers certainty and some stability up to a point which is why the civil service always loved it. But it does not make good the principles of devolution and maybe it is just impossible for the UK to ever make that so. Modern history certainly suggests as much.

The divergence of the politics of Scotland and the politics at Westminster has probably never been starker. The potential appointment of Boris Johnson as leader will only drive a greater wedge.

On domestic priorities as well as our place in the world it is clear that the vast majority of people in Scotland want no truck with the Trumpian, Johnsonian and

Faragian world view and approach. But that is what has dominated our public discourse and is set to continue to.

Lest we forget this would be a prime minister who thinks spending money in London is better for Scotland than spending money in Scotland itself.

For the first time in my life opinion research demonstrates that most Scots think that independence will be better for the Scottish economy in the long-term. Watching the continuing Conservative farce at Westminster should make most reasonable people think that this is now a far more urgent matter.