Dominic Raab’s tenure as Brexit secretary in 2018 was short and fruitless. He negotiated nothing in Brussels and resigned in protest, as if the failure was not his own. It is worth recalling that record now because Mr Raab has temporarily risen to the highest office, which is higher than his capabilities should allow.

Acting as prime minister during Boris Johnson’s illness is an unenviable task. The stand-in did not take decisions he must now defend, and has no executive authority to fix mistakes. Mr Johnson’s absence can be felt as drift and incoherence, expressed most potently in confusion over coronavirus testing and supplies of vital medical equipment.

Keir Starmer raised both subjects in his Commons debut as Labour leader on Wednesday. On both fronts he exposed the void where Mr Raab must have wished he had answers. The foreign secretary floundered most under questioning on testing, where the rate lags far behind what would be necessary to hit the target of 100,000 per day by the end of this month. He attempted a sleight of hand, defending the government’s record in terms of elevated testing capacity, an easier metric and not what had initially been pledged. Mr Starmer’s efficiency in identifying and dismissing that trick bodes well for when it is Mr Johnson at the despatch box and not his understudy.

On equipment supplies, Mr Raab’s defence was propped up by two flimsy planks: first, that no country is managing without difficulty; second, that every decision has been taken in accordance with the best available scientific advice. If there was ever merit in those claims it has worn thin from overuse by ministers evading responsibility for the lethal consequences of their actions – and inaction. It is disingenuous and improbable to suggest that ministers have followed a technocratic template, impeded only by logistical challenges beyond their control. Political prejudice infiltrates most decisions in government and Mr Johnson’s Downing Street is one of the most ideologically driven, politically cynical administrations in British history. It is likely that medical expertise was heeded, given that no one in the cabinet had relevant qualifications, but the equivalent skills deficit in other areas has never stopped the prime minister from having a strong opinion and acting on it before. Brexit is a case in point, where decisions of national importance were routinely taken in disregard of advice from people with professional expertise in the relevant fields.

It is plausible that the scale of the coronavirus threat forced ministers to set ideology aside. The Treasury response demonstrates that much in its swift abandonment of orthodox Conservative fiscal policy. But it is also feasible that Mr Johnson and his team took longer than necessary to climb out of some ideological trenches because they had dug themselves in so deep. That lag might help clear up confusion surrounding an EU procurement scheme for medical equipment, which Britain either joined or did not join for reasons that mysteriously vary depending on whether it is a civil servant, a minister or Brussels accounting for events.

On Tuesday, a senior foreign office official told a parliamentary committee that the decision not to participate had been political. Hours later he “clarified” to the contrary, but his written retraction contained no clarification of facts. The truth will surely emerge one day, probably in front of a public inquiry.

Meanwhile, the episode reinforces the impression of a government that was ill prepared for a crisis that demanded competence more than rhetorical bluster, and is failing now to get sufficient grip and undo damage done. Partly that is a symptom of over-centralisation and reliance on the individual authority of the prime minister, whose focus is necessarily elsewhere. But capable ministers and a resilient administration would be compensating better for Mr Johnson’s absence. That they are not, that the whole system seems obviously adrift, running on bluster and improvisation, testifies to flaws. Mr Raab is obviously out of his depth. Sadly, it seems his painfully shrunken stature is an accurate measure of the government he currently leads.