When you contemplate the conflict over drugs policy between the UK and Scottish Governments, what comes most readily to mind?

I would imagine that the concept of asymmetrical devolution is fairly far down the list. And yet it is decidedly relevant.

You know the basics, of course. Faced with a tragically high death rate, the Scottish Government wants to pilot a drug consumption room in Glasgow where addicts could get access to narcotics and help. But policy in this area is reserved to Westminster. And Westminster says no.

I am somewhat sceptical as to the proclaimed benefits of this plan. However, a sensible UK approach, as now endorsed by a Commons committee, would be to permit a pilot.

At the very least, that would remove any tiny temptation for Scottish ministers to use the Westminster obstacle as an excuse for Scotland’s lamentable record in this field.

One big snag is that it might take years to assess a pilot in any serious way. Few policies are granted years to mature in our short-term politics.

Consider, though, the source of this dilemma. For England, the UK Government is responsible for health care, the criminal law – and drugs policy.

For Scotland, because of devolution, Scottish ministers face public scrutiny over health and crime – both elements of the drugs issue. Yet they have no direct power over drugs action itself.

It is a mismatch. It is asymmetrical. It is the underlying cause of the tension between Holyrood and Westminster.

Now, it is definitely the case that such tension is exacerbated by wider conflict. SNP ministers yearn for independence. Tory ministers dream of defending the Union.

But this tension is also intrinsic to shared power. There were disputes between the then Labour UK Government and the first coalition Executive in Scotland.

Globally, such competition is common. In Germany, between the Federal Government and the Länder. In the USA, between Washington and the individual states. Indeed, the origins of the two big American parties lie in competing visions of power distribution.

In both these cases, however, there is a relatively clear demarcation between the two tiers. Here, Scottish ministers itch over the constraints of devolution while the UK Government tends to assume unquestioned primacy.

One should not over-state this. For the most part, ministers and officials co-operate where it is necessary and mutually advantageous.

Only this week, the Scottish Government agreed to endorse UK border controls on the importation of goods to protect biosecurity.

Intriguingly, there was also a deal on projects to reduce drugs deaths – with £4.5m contributed by the UK Government and £500,000 coming from Scottish funds.

Consider the political aspect. The Conservatives want to protect the Union. Hence their constant emphasis that “Scotland has two governments”.

But strategists in Tory ranks are also well aware that they have to defend devolution, embedding it within a Unionist construct. Opposition to Scottish self-government almost obliterated their party in Scotland in the past.

On the SNP side, they have long pursued a cautious approach. They seek to govern moderately and sensibly within the limits of devolution while simultaneously arguing how much more they could achieve with the full powers of independence.

Now, these twin tactics are under strain. There are one or two voices in Tory ranks – only one or two – suggesting that devolution should be restricted, even reversed.

On the SNP side, there are more than a few voices saying that a more radical approach is required in order to advance the cause of independence.

How does this manifest itself in practice? On the SNP side, strategy is still inchoate as the movement decides what to do in the absence of indyref2. A de facto referendum at the next election? Withdraw from Westminster? Nothing fixed yet.

The Unionist approach is to emphasise the Union. UK ministers bypass Holyrood in some limited cases and badge projects in Scotland as being funded by Westminster.

They exercise power over the devolved structure, for example by vetoing Holyrood’s gender recognition reform law.

That veto will soon be tested in the Court of Session. Scottish ministers may be torn. Instinctively, they want to overturn that UK block. Privately, they might shed few tears if the gender issue were to slip from the political spotlight.

More generally, though, there are SNP complaints of a UK Conservative power grab assailing Holyrood. I note the evidence of a more active and persistent UK polity. However, I question whether this complaint has all that much traction with the Scottish public.

Still, tension there is, leading to breaches of protocol. The Health Secretary at Westminster offers to intervene over Scottish waiting lists. The Scottish Health Secretary offers to mediate in the English doctors’ pay dispute. To both of them, I say: play nicely.

A dilemma arises for the Scottish Tory leader Douglas Ross. He cannot disown his UK party colleagues – but he needs a Scottish policy dimension.

This week he urged Scottish tax simplification. So much, so familiar. But he went further. He said that Scotland should be fiscally competitive within the UK.

That might mean undercutting the Treasury on income tax. Which, if enacted, would depart from the cautious tone deployed by Scottish Tories in the past.

However, Mr Ross remains firmly Unionist. He wants a joint operation, involving Scottish and UK ministers, to drive growth and wealth.

I am certain Mr Ross is sincere in this endeavour – and it fits the “two governments” mantra. But I can see problems within our asymmetrical structure of governance.

UK ministers might be intuitively inclined to see such a system as a delivery mechanism for Treasury policy. Scottish ministers might tend to jib at such direction.

Plus, the current Joint Ministerial Committee set-up scarcely suggests that co-operation emerges from formal discussions. Quite the reverse.

Equally, though, those in power can sometimes share interests, despite partisan differences.

For example, both the UK and Scottish Governments will be keen to co-operate over the Covid inquiries, hoping thereby to facilitate open discussion – and avoid censure.

More generally, though, tension is likely to persist. Perhaps, on occasion, it is healthy. To govern is to choose. Sometimes it can help to have alternative voices joining the discourse.