SADLY, we’ve been here before and know how a political drama like Nadhim Zahawi’s usually ends.

The script goes something like this: screaming headlines about allegations of wrongdoing are firmly denied and calls for full transparency are met with a disdainful “nothing to see here, Guv” response.

Cast-iron reassurances are given as opposition parties’ demands for an official inquiry are rebuffed; until, that is, pressure forces the Government to cave in.

And, finally, after the inquiry reports, the minister – usually snapped looking grim-faced in the back of a government limousine – is forced to resign in disgrace.

So now, Rishi Sunak’s extended baptism of fire continues. Understandably, the Prime Minister is “livid” with his Treasury successor given his determined attempt to draw a line under the Boris Johnson era of dishonesty, having promised to govern with “integrity, professionalism and accountability”.

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Yesterday, the PM was hosting his Cabinet chums, including the beleaguered Conservative chairman, at his country pile in deepest Buckinghamshire to magic up a plan to win the General Election. Mr Zahawi, whose role would normally put him at the helm of the party’s election campaigning, was not expected to play a significant role at the Chequers meeting. Which says something.

In politics, perception isn’t everything but from time to time it comes pretty close.

Sir Laurie Magnus, Mr Sunak’s ethics adviser, is looking into whether the Stratford-upon-Avon MP broke the ministerial code whose general principle is that ministers are expected to uphold the “highest standards of propriety” and “ensure no conflict arises, or could reasonably be perceived to arise, between their public duties and their private interests, financial or otherwise”.

So, what’s important is not just the reality of a situation but also the perception of that reality.

And yet in the Zahawi case we don’t even have to rely on our perception because some facts are already known.

For example, we know Mr Zahawi avoided paying more than £3 million in tax owed to the public purse. Not only that, he was fined another million or so for his “carelessness”, which translates into everyday language as negligence. And not only that, he did so while he was Chancellor of the Exchequer; the minister in charge of the tax system. You couldn’t make it up.

Yesterday, Jim Harra, the HMRC boss, didn’t help the Cabinet minister’s cause when he told MPs, regarding tax compliance, there were “no penalties for innocent errors”.

Furthermore, we know this run-in with the taxman somehow slipped Mr Zahawi’s mind when he gave the PM reassurances about his tax affairs. Which meant last week Mr Sunak was left out on a limb when he told MPs his Cabinet colleague had answered all matters about his tax affairs “in full,” when he did nothing of the kind.

Then there is the little matter of the Cabinet Office vetting process. How could its propriety and ethics team have missed the Tory chairman’s contretemps with HMRC? Or did it?

Surely, civil servants must have mentioned this to the man who made Mr Zahawi Chancellor? But then that man was Boris Johnson. Some might argue that the question answers itself.

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Whitehall sources indicate Cabinet Secretary Simon Case, the Civil Service chief who cleared the under-fire minister for his numerous government roles, is thought to be in a slow-motion exit and will be gone by the summer.

During Prime Minister's Questions, the most interesting aspect of this week’s bruising encounter was how Sir Keir Starmer sought to link Mr Sunak’s handling of the Zahawi row with the PM's billionaire wife Akshata Murty, who has held non-domiciled status, which could have significantly reduced her UK tax bill. The Labour leader twisted the knife, telling MPs: “We all know why the Prime Minister was reluctant to ask his party chair questions about family finances and tax avoidance.”

Suggesting the Number 10 job was “too big” for Mr Sunak, Sir Keir then pressed his favourite button, adding: “His failure to sack him when the whole country can see what’s going on shows how hopelessly weak he is; a Prime Minister overseeing chaos, overwhelmed at every turn.”

Later, the PM’s spokeswoman steadfastly refused to say if her boss had ever had to pay a penalty to HMRC, stressing a person’s tax matters were “confidential”. But once the chief comrade’s office had made clear their man had never had to pay such a penalty, Downing Street relented and said neither had Mr Sunak.

With more revelations about the bullying claims hanging over Dominic Raab – which the PM’s deputy denies – suggesting they now involve some 24 civil servants and yet another row concerning Mr Johnson – taxpayers face stumping up £222,000 in legal fees for the ex-PM’s defence against allegations he misled Parliament over Partygate – Mr Sunak could be forgiven for feeling the Downing Street walls are closing in on him.

Now, we eagerly await the report of his ethics tsar. Despite even many Tory MPs privately believing otherwise, it’s possible Sir Laurie could remarkably clear the party chairman, who has repeatedly insisted he is “confident” he has “acted properly throughout”.

Intriguingly, Downing Street pointed out how the ministerial code had recently been updated, “so it’s no longer a binary decision”. An escape route, perhaps? It must be remembered the PM reappointed Suella Braverman as Home Secretary just days after she quit the Cabinet – for breaking the ministerial code.

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The PM, we’re told, wants the Magnus report on his desk within days, so that if he were to have to jettison his Cabinet chum, the political damage could be absorbed as quickly, and as far away from the May local elections in England, as possible.

Given what we already know, it seems inescapable to conclude Mr Zahawi is following a well-trodden path of many previously less-than-transparent ministers, making him, to use a technical term, toast.

After his widely-regarded triumph in helping to speed up the Covid vaccination programme, the party chairman’s forced departure would mean his most telling contribution to the Conservative Government’s electoral cause will be to hammer another nail in its coffin.