Even at the height of his popularity, Boris Johnson routinely avoided close questioning – to the extent of once hiding in a fridge to dodge a TV inquisitor. The former UK prime minister is likely to be dreading next week’s appearance at the Covid inquiry. And he probably should. It is no exaggeration to say that events on Wednesday and Thursday at the inquiry’s repurposed office building in Paddington, west London, could help define the post-power image and legacy of Johnson, and very possibly not for the good. This most congenitally elusive of politicians, who thrived in the one-question-at-a-time discourse of the Commons but was deliberately shielded from detailed media interviews, faces at least 12 hours of questioning by one of the country’s top barristers, Hugo Keith KC. All this will be done under oath, in the glare of attention from the media and bereaved relatives, and in a detail that will not be lost on Johnson, using an inquiry template set up by the then prime minister himself. When, in May 2021, Johnson announced a public inquiry into the pandemic, his decision that it would start taking evidence no earlier than spring the following year was widely seen as an attempt to kick the issue into the political long grass. Two and a half years on, we are now deep into that grass, and Johnson, rather than contemplating his path towards a second term in No 10, is instead a much-discredited former prime minister and ex-MP. Now he faces a possible demolition job in one of the few policy areas to which he and his allies still cling: that on Covid he “got the big calls right”. Allies of Johnson say his approach will be to accept some mistakes happened, and to take responsibility, rather than shift the blame to others. At the same time he will argue for areas he does view as a success, such as the vaccine rollout and the pace at which the UK economy reopened. He is also expected to stress his role as prime minister in balancing the competing claims put to him, and to point to ways the structure of government could be improved for a future pandemic. Johnson has spent months preparing for these two days, poring over thousands of pages of evidence put to him by the inquiry. While he has not seen every document, the expectation is that next week will focus more on the machinery of government rather than more revelations about personality clashes. Presenting his case will be a tricky moment for Johnson. The current module of the inquiry covers decision-making at the top of government, and the spotlight shone so far by other witnesses into Johnson’s Downing Street has been stark and unforgiving. Listening to not just avowed Johnson foes such as Dominic Cummings but a range of officials, civil servants and ministers, even those sympathetic to him, leaves the definite impression of a prime minister barely capable of making any calls at all, whether right or wrong, instead buffeting chaotically on the currents of others’ opinions. The direct glimpses of Johnson thus far have been rarely flattering, whether through witness evidence or extracts from the diary of his chief scientific adviser at the time, Sir Patrick Vallance. As well as his chronic indecision and changes in opinion, the unfiltered Johnson can sound glib and thoughtless, arguing to lift lockdowns on the basis that the older Britons most vulnerable to Covid “have had a good innings” and that the virus was “just nature’s way of dealing with old people”. One of the most damning such vignettes came from Edward Udny-Lister, Johnson’s chief of staff during the pandemic and one of his longest-standing political aides. Lister directly contradicted the word of his former boss by confirming that in autumn 2020 Johnson said he would rather “let the bodies pile high” than impose another lockdown. Johnson can, and almost certainly will, argue that no prime minister would emerge unscathed from such wholesale scrutiny, including gossipy WhatsApp messages that were, like Vallance’s diary, never intended to be seen by others. The problem Johnson faces, which he will try to push back against next week, is the way these revelations have proved not just embarrassing, for example his seeming inability to follow scientific concepts, but are at times unsettling, even alarming. Chief among these has been the gradual portrayal of the wider Downing Street operation Johnson allowed to operate around him, one described variously as a “culture of fear”, “poisonous” and “mad”, as well as rife with violent and misogynistic language. Much of this perceived toxicity centred on Cummings, who was generally viewed as dominant and in charge. Perhaps the standout evidence so far was extracts of messages between Mark Sedwill, who started the pandemic as cabinet secretary, the most senior civil servant in the UK, and Simon Case, the man who succeeded him and who is still in the job. In a notably damning detail, Case said he had told Johnson at one point that replacing a senior No 10 official had proved difficult because “lots of the top-drawer people I had asked had refused to come because of the toxic reputation of his operation”. Covid-19 Bereaved Families for Justice – who will get the chance to question Johnson through their barrister – said among areas on which the group will want answers is why the first and second lockdowns were called when they were, and how policy was affected by the culture inside No 10.