IF you believed everything that was said to MPs by Dominic Cummings this week, then the government of the world’s fifth largest economy is run less competently than a frat house, with as few ethical qualms.

It left a mountain of questions. But the biggest was this: how much of it was true? Mr Cummings is a man motivated to seek revenge and his testimony was low on credibility in key respects. He painted a two-dimensional picture of government. All the players in his tragifarce were either heroes or duds. No one was doing their best in difficult circumstances; no one was making good decisions alongside the bad.

Mr Cummings’ downplaying of his own power within government felt highly expedient, and was undermined by his boast at having installed Simon Case as permanent secretary at Number 10. His claim that behavioural scientists insisted the British public would not accept a tough lockdown was promptly undermined by minutes from a government committee of behavioural scientists suggesting the opposite. He has a new nickname originating with a government insider: DLF, which stands for disingenuous little… you get the gist.

And yet, undeniably, some of his blunderbuss testimony rang true. Boris Johnson vacillating over decisions like an errant shopping trolley? What, the man who u-turned on policy decisions a dozen times between March and December last year, and got into a fight with Marcus Rashford not once but twice? Surely not, says absolutely no one. Boris Johnson unfit for office? Half the parliamentary Tory party feared that when they voted for him as leader.

It is all too easy to believe that the Prime Minister resisted a circuit-breaker lockdown in the autumn, against scientific advice, because of economic concerns. We already knew that there was effectively a herd immunity strategy at the start of the pandemic, that his government’s preparedness was drastically below par and that bad decisions were made about the discharge of patients from hospitals to care homes. Dominic Cummings has just added colour.

But then there were other statements which have left us wondering. The most damning was this: that tens of thousands of people died who didn’t need to die.

Strip away the politics, the backstabbing and the individual failings, and that is what matters: did poor decision-making and skewed priorities cost lives?

Relatives of the 128,000 Covid dead cannot possibly be left waiting indefinitely for an answer. Labour and the SNP are calling for a public inquiry taking in the Covid response of all four home nations to start quickly, this year not next, and the case in unarguable. The pandemic continues; there could be another crisis at any time, God help us. It’s no good writing a history thesis about what went wrong in a year or two, when memories have dimmed, we need a handbook right now.

Mr Cummings may be an unreliable witness but so grave are his allegations that the government cannot simply be allowed to bat them off – or so you might think.

Enter Matt Hancock, the main target of Dominic Cummings’ ire and disdain.

Mr Cummings portrayed the UK health secretary as a serial liar and a poor minister who should have been fired over “15 or 20 things”.

That being the case, Mr Hancock needed to dispel the doubts and smooth furrowed brows when he came before the Commons yesterday. You felt he wanted to be written up as “relaxed”, the hard-working minister wearied but unflustered by a fantastist’s attacks.

But the impression he left after an hour at the despatch box was more of arrogance and reticence. His only direct statement on Cummings – that these “unsubstantiated allegations are not true” – was vague and he avoided directly answering detailed questions around the specific allegations, such as the suggestion he’d told Downing Street in March patients were being tested before discharge into care homes when in fact they weren’t. He fell back time and again on the line that he’d answered such questions many times before.

Was it Hancock that was lying, or Cummings – or both? Someone must be, but so far, we can’t tell which.

When asked by the SNP’s Chris Stephens if Mr Hancock agreed that a public inquiry should be brought forward to avoid key people rewriting their memories or losing documents, he barely deigned to get off the bench, answering with a clipped “no” and then sitting back down.

I wonder how respected the families of the dead felt to witness that.

We can’t know exactly what Mr Hancock said to the Prime Minister; what we can do is check the veracity of some of the health secretary’s other claims, such as his assertion that there was never a national shortage of PPE (actually the evidence suggests there was, said the fact-checking charity Full Fact on BBC Radio Four, pointing to a National Audit Office finding that English health trusts only got a third of the aprons they needed at the peak last year) or that he put a “protective shield” around care homes (care home managers from around England have been lining up to share their experiences of being made to take patients, untested, into their care homes in the early months of the pandemic).

Why does this retrospective blame game matter so much? Because all those whose loved ones have lost their lives have an absolute right to know what went wrong.

Because Mr Hancock and Mr Johnson are still in charge, the pandemic isn’t over, and the recovery is still to come.

And because the public need to know if the people sitting around the Downing Street cabinet table are fit to be there.

The public has been forgiving of all four nations’ governments during the pandemic, recognising that mistakes will be made in difficult times, but politicians know that forbearance has limits. The former head of the civil service Lord Kerslake, speaking yesterday, stressed the importance of that public inquiry. The unprecedented challenges people faced did not “explain or defend some of the decisions that were made”, he said.

Here in Scotland too the decision-making process needs to be laid bare and here too it will be a tough process for political leaders. Here too the level of care home deaths was appalling.

It will be painful, but it needs to happen, and soon.

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