AT his Christmas reception in 2008, Alex Salmond laid on a mouth-watering selection of curries for Scotland’s political journalists in Bute House.

Discovering how well this had gone down with the easily pleased hacks, Scottish Secretary Jim Murphy tried to outdo him the following year by providing a slap-up curry at his own festive bash.

This was before austerity started to bite and relationships soured: by the time Mr Salmond left office, journalists were treated to bowls of crisps in the basement of St Andrew’s House.

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But during the three years when Scotland had an SNP government in Edinburgh, and a Labour government in Westminster, there was a newfound rivalry between the Scottish Government and the Scotland Office.

Until Mr Murphy took over, the job of Scottish Secretary had – literally – been part-time.

When the future Scottish Labour leader was appointed by Gordon Brown, it became the full-time role it is today.

According to SNP figures, communications staffing costs for the Scotland Office have soared from around £100,000 in 2007-08 to over £700,000 a decade later, and yesterday there was a fresh row about the department’s spending on overseas travel.

The Nationalists have said this is justification to abolish the department, complaining that it’s spending public money "pumping out propaganda" promoting Scotland’s place in the UK.

The reality, of course, is that this is what governments do. The Scottish Government is also spending public money promoting Scotland with its effective "Scotland is Now" tourism campaign – ostensibly aimed at a global market, but clearly serving a dual purpose by suggesting to the domestic market that Scotland’s values are distinct.

The political tensions that started under Salmond and Murphy have continued, with present incumbent David Mundell facing near-weekly calls from the SNP to resign, often without much of an explanation as to why he should fall on his sword.

Intergovernmental relations between the UK and Scottish governments are "under pressure like never before", according to SNP MP Pete Wishart.

Mr Wishart acknowledged that work between civil servants is "conducted perfectly well", and that is certainly what those behind the scenes insist is the case.

If there is a problem, then, it’s among the politicians, and that’s hardly surprising – and not really anything new.

It takes two to tango.

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The SNP’s well-worn narrative about a dysfunctional Westminster system doesn’t stand up to scrutiny if the political leaders work in harmony together. There is every reason for the SNP to be perfectly happy that intergovernmental relations are considered "under pressure like never before".

After all, the Scottish Government’s stated aim is independence and the abolition of intergovernmental relations with the UK.

But the UK Government’s stated aim is to preserve the Union, so it is unsurprising that the role of the Scotland Office has steadily increased over the years.

And if tensions are strained now, it’s only going to get far worse.

One of Theresa May’s final acts of her premiership was to announce a review of the way the UK Government handles the current devolved settlement.

That doesn’t mean a shake-up of powers as some initially thought; it means a shift in mindset for every single UK Government department.

Today, Whitehall civil servants are told to ensure their work fits in with the devolution arrangement – is the Scottish Government kept engaged? How does the Sewel Convention apply?

In the future, the questions will be: Does our work strengthen the Union? Or does it potentially advance the case of independence – and if so, let’s think again.

Will it make the UK civil service more politicised? Probably.

But that happened long ago here in Scotland.

Last year, the Scottish Tories complained that civil servants were contacting witnesses ahead of appearances at a Holyrood committee, and highlighted graphics being tweeted by Government accounts which "used the SNP’s party political language".

Valid concerns at the time, but such complaints are likely to appear hypocritical in the near future.

And it’s not just civil servants who are being told to change their mindset – Cabinet ministers are too.

The message is clear: if the Union is to be saved, the UK Government needs to loosen its purse strings in Scotland, as The Herald exclusively revealed last week.

That includes splashing the cash in both reserved and devolved areas – the Edinburgh City Deal for example has delivered cash for the capital’s university; and the UK Government is helping fund Edinburgh’s new concert hall, even though culture is devolved.

The argument is that such a venue is of cultural importance for the entire UK. Expect much more of the same to follow.

Current Chancellor Philip Hammond has been a bulwark against this ever since he moved into Number 11, arguing that it’s unfair on English taxpayers as Scotland already receives its share of funding through the Barnett formula.

It means spending money twice over north of the Border, he complains, with some justification.

But the order has now gone out loud and clear that this is the price to pay to save the Union.

And nobody has done more to achieve this mindset change than David Mundell.

He has spent years quietly and effectively persuading his Cabinet colleagues of the risk to the Union and explaining to Whitehall departments they must learn to understand devolution.

Next week, just moments before Theresa May’s final PMQs before she heads to the palace will be the last Scottish Questions before summer.

No fan of Boris Johnson, it could be Mr Mundell’s last appearance at the despatch box.

But if Prime Minister Johnson wants to avoid going down in history as the man who lost the Union, he would be well advised to consider keeping Mr Mundell in post.

He should ask himself who does Nicola Sturgeon want as Scottish Secretary? The assured David Mundell or a maverick like Ross Thomson? The First Minister would surely prefer the latter.

But whoever is Scottish Secretary, the role is now crucial to Scotland’s constitutional future.

It’s a far cry from the part-time job it was before the SNP stormed to power.

There will be more money to spend in Scotland; far greater UK Government involvement in Scotland – and more explosive political rows with the SNP as a result.

The great unknown is which government will emerge as the political winner in this latest constitutional battle.