IT was the frostiest of stares that Liz Truss gave Nicola Sturgeon as the First Minister spoke during the Queen's service of prayer and reflection at St Giles’ Cathedral in Edinburgh.

The iciness came as no great surprise given the PM dismissed the SNP chief during the heat of the Tory leadership contest as a mere “attention-seeker,” who should best be ignored.

While the FM was more publicly magnanimous, suggesting she wanted to work “constructively” with Truss, there seems little chance sisterly love will break out between Edinburgh and London, particularly as the political temperature rises in the run-in to the 2024 General Election.

The icicles at their first formal meeting, wherever it is, will be difficult to sweep away.

The party conferences, now almost here, are ritual occasions for political leaders to mount the stage and lash out at their opponents; outside – and inside – their parties.

Coincidentally, as the SNP’s annual get-together next month draws to a close in Aberdeen, just hours later, the legal battle at the UK Supreme Court in London is due to begin over Indyref2.

Sturgeon’s keynote speech will once again be based on her full-throated denunciation of Whitehall’s attempt to “deny Scotland democracy”. It will follow Truss’s own conference address of a few days earlier when the newly-minted Conservative leader will have lovingly extolled the virtues of the “precious Union”.

For some time, many senior Conservatives urged Boris Johnson against promoting so-called “muscular Unionism,” to, rather, hug closely the nationalists and appear uncomfortably reasonable even when the SNP leadership unreasonably displayed its own muscular nationalism.

One suspects, however, Truss doesn’t do cuddly; she described Welsh Labour’s Mark Drakeford as a “low-energy version of Jeremy Corbyn”.

She is more likely to adopt the Lord Frost up-and-at-‘em approach. He recently raised eyebrows by suggesting the Scottish Government was a “subordinate entity” to Westminster’s “supremacy” and that breaking up Britain would be “morally wrong”.

However, following last month’s SNP outrage at Truss’s snipe at Sturgeon, it has to be pointed out the FM is no stranger to unleashing her own barbs against political opponents.

She once mocked David Cameron as “pig-headed” and recently branded Johnson the “worst Prime Minister…in my lifetime” even though, politically, the blond Beatle was political manna from heaven for Sturgeon.

Indeed, Truss must be aware, if she adopts a bare-knuckle approach, she will be engaging in political street-fighting with someone who has several championship belts.

In the run-up to the independence referendum, Nick Clegg dumped the urbane Michael Moore as Scottish Secretary – no doubt, prompted by Cameron – saying euphemistically a “different experience” had to be drawn upon.

The move followed the Lib Dem Cabinet minister being duffed up – metaphorically – during a TV head-to-head with the SNP leader. He was replaced by the “no nonsense” bruiser Alistair Carmichael, who, it was hoped, would land a few punches on the Sturgeon chin.

Yet, to his embarrassment, during another TV debate he too was duffed up – metaphorically – by Sturgeon. The lesson had been learnt.

Amid the blanket coverage of the Queen’s death, it’s natural for people to ponder what it means for the survival of the 315-year-old Union.

Labour peer Lord Robertson, the ex-Nato Secretary-General, popped up on the airwaves to confidently assert King Charles was “determined to make sure the Union stays together”.

In the opposing corner, Alba leader Alex Salmond hit out at BBC “bias,” claiming it had “badly let down” viewers by appropriating “a display of Scottish respect and affection for our late monarch to peddle a state political line”. Namely, that HMQ was pro-Union and staunchly anti-independence.

The former FM accused reporters of “parading their historical ignorance but apparent certainty of the late Queen’s opinions without the benefit, for the most part, of ever having a serious personal conversation with her”.

Earlier, Nicholas Witchell, the BBC’s royal correspondent, claimed the Queen was “greatly distressed” about the prospect of an independent Scotland and said Charles, Prince William and the whole royal family felt “very strongly about the importance of the Union; all the advantages the nation as a whole has from being united”.

So, it may be in her audiences with SNP chiefs the Queen displayed a deft diplomacy often missing in others.

Given her remarks during the 1977 Silver Jubilee when she told MPs and peers about the “benefits which Union has conferred…on the inhabitants of all parts of this United Kingdom,” the Crathie Kirk incident in 2014 when she urged Scots to “think carefully” about the forthcoming referendum and Cameron’s claim about how the Queen “purred down the line” when she was told the poll result, it’s hard not to conclude that she was strongly pro-Union.

Also, given his role, it’s hard to imagine, as he completes his tour of the Union today in Wales, that Charles is not of the same opinion.

No one, of course, can be sure of the impact that the Queen’s death will have on the Union debate. But his constitutional eminence, Professor Sir John Curtice, suggested it would “probably not” have any.

Timewise, more pertinent perhaps is what the coming months will mean for the political futures of Sturgeon and Truss.

Unprompted, the FM recently dropped the idea into the public consciousness that she might not be around for much longer on the political frontline. By the 2024 election, she would have been FM and SNP leader for almost 10 years; a convenient peg on which to hang her ministerial boots.

And if Truss fails in the formidable task of unifying her party and steadying the economic ship of state in just 18 months, then her future on the political frontline will be terminated by the public.

It could be in the General Election aftermath both party leaders will pass through the door marked exit and a new generation will take over.

In the electoral cycle, the most powerful political slogan is “time for change” and as we have witnessed with some sadness this past week, change is constant.