JUST when you thought the Downing St dysfunction couldn’t get any worse, something else happens.

One has to wonder when Simon Case, Britain’s top civil servant, took on the role as HMG’s chief bloodhound in the “partygate” probe, he didn’t ponder how it might not look terribly good if the “Christmas Party,” which had occurred in his own office, was ever made public. The mind boggles.

As Boris Johnson’s administration continues to churn out the banana skins, Keir Starmer and Ian Blackford are laughing all the way to the polls.

Indeed, it was Westminster’s Nat-in-Chief, who was quickest out of the blocks on Friday night when claims emerged of two gatherings in the Cabinet Office when social mixing was banned.

The Highland MP called on Case to resign and suggested the latest revelation would confirm the public’s view that his inquiry was “rigged” and meant to “dodge accountability”.

Blackford, who recommended a judge should now head the partygate probe, twisted the political knife, declaring: “This is a government that stinks of corruption and stinks of sleaze.”

A Cabinet Office source explained an office quiz had taken place on December 17 2020 but was “absolutely not” a party before admitting Case had been aware it was taking place but had not participated. Yet the damage was done and the inevitable happened.

Downing St sent out a concise note, announcing Case had “recused himself” from the official probe to ensure it “retains public confidence”. Sue Gray, a top, no-nonsense official at Michael Gove’s Levelling-Up department, who, by happenstance, was previously the Cabinet Office’s ethics tsarina, is taking over, and, said Number 10, would “ascertain the facts and present her findings to the PM”.

As the partygate probe takes on the feel of a Carry On farce, one can only hope Gray has made clear to herself that she did not party in Downing St last year, virtually or otherwise.

Ironically, only hours earlier, Oliver Dowden, the Tory Chairman, took to the airwaves to boldly assert he was “confident” the Case investigation would “vindicate” the PM and his repeated assertion that no restrictions had been breached.

I wonder, following the Cabinet Secretary’s embarrassing withdrawal, if Dowden is now quite so confident. The hapless Boris might believe he can, as the saying goes, bounce back better. But the odds are stacking up against him.

Following the disastrous but predictable North Shropshire by-election result, the siren voices emerged. Ruth Davidson, the ex-Scottish Tory leader, claimed the PM was “drinking in the last chance saloon” after being “put on warning by his MPs”.

The peer insisted colleagues were “looking for a bit of bloody grip to be exerted”. Sir Roger Gale, the veteran Conservative, noted how there had been two strikes against Boris and that a third meant he would be out.

Given Johnson’s track record of mistakes and misjudgements, it seems only a matter of time before this happens. Scottish Tories have known for some time that the PM is an electoral liability north of the border – hence his conspicuous absence in the run-in to the Holyrood elections in May – now it seems English Tories are beginning to feel he has become one south of the border too.

For the past few weeks Labour has been ahead in 13 out of 15 opinion polls, at one pointing gaining a 9% lead.

At every turn, Starmer has not missed an opportunity to place the political emphasis on leadership or, rather, what he regards as Boris’s lack of it.

Tory MPs have helped the Labour leader in this pitch by opposing the PM on the issue of vaccine passports; meaning the chief comrade can insist he is putting the national interest before party politics by supporting Government restrictions.

Yet, of course, such a move has a deeply significant political impact. The latest political problem for Boris is, as Omicron zips through the country at a startling rate, the UK Government’s scientific advisers are recommending even tougher measures for England, such as banning indoor mixing in a two-week “circuit breaker” lockdown post-Christmas.

Of course, Plan C could mean a festive recall of Westminster, which would mean the politics getting worse for Boris but better for Keir. And yet, looking longer term, the Labour knight should be careful what he wishes for.

If he believes - and he does – the PM is a busted flush, the Tories at some point will almost certainly ditch the Brexiteer-in-chief and could get in place someone who is more adept at managing things and less enthusiastic about Peppa Pig or impersonating a car engine.

Sir Graham Brady, the normally inscrutable Chairman of the 1922 Tory backbench committee, has informed his colleagues of a change to the normal rules; they can email in calls for Johnson to go over the Christmas break; 54 is the magic number to trigger a vote of no confidence.

The sharpening of knives can be heard across Westminster but their use could be held back a while.

Summer tends to be the preferred defenestration period because there is often a natural political lull, which gives a new incumbent time to rearrange their Cabinet and map out their policy priorities before the launch-pad of the autumn party conference.

Such a timescale would give a new Tory leader and the new PM the best part of two years before the next scheduled General Election in 2024; enough time, some might think, to turn Conservative fortunes round.

So, helping to get rid of Boris two years out from an election could turn out to be Starmer’s biggest mistake; Rishi Sunak, the Chancellor, or Liz Truss, the Foreign Secretary, might prove, electorally, to be a more formidable opponent.

This week, one senior Tory source, who was a minister in the May Government, suggested Boris was a goner, likening his premiership to the Hans Christian Andersen tale of the king’s new clothes. He told the Politico website: “Once you’ve seen that” - the PM naked, politically speaking of course - “you can’t unsee it.”