It is marked in calendars around Westminster and Whitehall as a day to dread. On 13 June, the public inquiry into the handling of the pandemic will start taking oral evidence. A procession of those at the heart of government decision-taking and blunder-making will be interrogated under oath about their actions and inactions. Heather Hallett, the retired judge in the chair, is said to be disappointed that she did not make lord chief justice. Yet there is surely no more significant role in her line of work than investigating, passing judgment and drawing lessons from the performance of government during the deadliest peacetime emergency in more than a century. This inquisition is not going to be a dry and bloodless exercise. The formidable judge is adopting a take-no-prisoners approach. We know this from the advance questions the inquiry team has been sending out to those who will be examined. Goes one scorcher to Boris Johnson: “In or around autumn 2020, did you state that you would rather ‘let the bodies pile high’ than order another lockdown, or words to that effect?” Goes another: “Please confirm whether in March 2020 (or around that period), you suggested to senior civil servants and advisers that you be injected with Covid-19 on television to demonstrate to the public that it did not pose a threat?” Goes a third zinger: “Did you say on or around 22 September 2020 that you felt that Sage had ‘manipulated’ you into imposing the first lockdown?” Lady Hallett correctly intends to bring an intense scrutiny to the conduct of our rulers and the calibre of the UK state during the pandemic. Some of the participants may emerge with their status burnished; others have ample reason to be fearful of the impact on their reputations of remorseless evidence-gathering about the many things that went wrong during a crisis that cost so many lives. Tories shiver that the inquiry, which is not due to complete its oral hearings until the summer of 2026, will haunt their party for years to come. Explaining what happened and why is a moral duty to the bereaved and especially to those with cause to think that loved ones might have survived had our country been better prepared for the pandemic and more ably governed during it. This inquiry cannot bring anyone back to life. The service it can perform for victims has been illustrated by earlier inquiries such as those into the Hillsborough disaster, the Bloody Sunday killings and the contaminated blood scandal. One of the vital functions of this public inquiry is to give a voice to the bereaved and supply a form of justice by forcing decision-makers to give account and take responsibility for what they did. Those who fail to learn from history are doomed to repeat it. A comprehensive inquest into the pandemic is essential to improve our chances of avoiding a repeat of the human, social and economic calamities inflicted by Covid-19. Some question the purpose of this inquiry on the grounds that the lessons have already been learned. I wish I could be confident of that. At Westminster and in Whitehall, lesson-learning has taken a very distant third place to arse-covering and excuse-mongering. The inside accounts we have been provided with so far, from the likes of Dominic Cummings and Matt Hancock, have been self-promoting and self-serving. The inquiry is the opportunity to gather testimony from the full cast of witnesses and compel the production of the entirety of the evidence. Absent that, we won’t get what we need, which is an understanding of why so many vital arms of the state cracked under the pressure of the pandemic and the centre was often in complete meltdown. To be sure that the inquiry gets at the whole truth, it is critical that Lady Hallett prevails in her battle with the government to make it hand over material that it doesn’t want her to see. The immediate point of dispute is a cache of texts and WhatsApp messages between Boris Johnson and 40 of his then lieutenants, among them Rishi Sunak, along with the contents of 24 notebooks of diaries that he kept while at Number 10. The Cabinet Office has taken the extraordinary step of going to court to try to block the judge’s demand to see this material. No one I have spoken to can think of a precedent for a government seeking to thwart a request for evidence from an official inquiry that the government itself set up. Ministers must think something huge is at stake to launch a gambit that looks so dreadful. Groups representing bereaved families are crying betrayal and the opposition is making accusations of a cover-up. Most legal opinion thinks the government will go down to a humiliating defeat because the inquiry was set up with a statutory remit that gives Lady Hallett a sweeping authority to demand the production of evidence. “They’re going to lose,” says one senior Tory. “Even in the unlikely event that they win in court, they will still lose because they will look guilty in the eyes of public opinion.” The Cabinet Office contends that it wants to deny access to the Johnson material because it is “irrelevant” to the inquiry. That’s not for it to decide. It is for the judge to judge what is potentially valuable to her investigations. Another of the government’s contentions is that it has a duty to protect “the privacy” of politicians and officials. That doesn’t wash either. The judge needs to know the context in which key actors were operating at the time when big calls had to be made. We already have good reason to think that the state of Mr Johnson’s personal life is extremely relevant to that. We know that he was finalising a messy divorce and scrabbling about to finance it when the pandemic started. It is absolutely legitimate for the judge to be interested in “the degree of attention given to the emergence of Covid-19 in early 2020 by the then prime minister”. The government claims that handing over this material will set “a dangerous precedent”. The argument goes that civil servants will stop giving frank advice and ministers won’t engage in candid debates for fear that private exchanges will be made public in the future. I might have more sympathy were it not for the fact that ministers constantly leak inside information when they think it suits their interests. The supposed duty to respect the confidentiality of private conversations is also regularly betrayed when politicians bang out their memoirs. So much for the government’s flimsy pretexts for attempting to hide this material. What and who is the Cabinet Office trying to protect? The messages and diaries may contain stuff that is excruciatingly embarrassing for Mr Johnson, but he has now done a reverse ferret by saying he’s happy for the judge to have all of it. The disgraced former prime minister probably has less to fear from this inquiry than some others, if only because his reputation has already hit rock bottom. There is a settled consensus that the pandemic was deadlier than it need have been because he was so useless at making decisions and presided over such a chaotically dysfunctional regime at Number 10. There are grounds to suspect that the Johnson cache contains things that officials are anxious to keep concealed. The exposure earlier in the year of Matt Hancock’s WhatsApp messages was acutely uncomfortable for the cabinet secretary, Simon Case, who was shown finding it “hilarious” that travellers were being “locked up” in “shoe box” rooms in quarantine hotels. The material is also highly likely to contain stuff that serving ministers don’t want in the public domain. “My hunch is that Sunak or someone else still in government feels at risk,” remarks a former member of the cabinet. The prime minister and his people are clearly nervous that the judge will next demand sight of all his pandemic texts and WhatsApp messages. It would not look good for him were it, for instance, to be revealed that Mr Sunak was warned in advance that his Eat-Out-to-Help-Out-the-Virus subsidised meals wheeze would be the plague-spreader that it turned out to be. The truth about that and everything else about the inner workings of government during the pandemic must be brought to light. The point of a public inquiry is to go deep and be thorough, forensic and unflinching. Lady Hallett is entirely right to demand access to any evidence that may be pertinent to her vitally important work and the government is wrong and looks desperate trying to conceal it. We must have full disclosure to keep the public faith and serve the public interest. Andrew Rawnsley is Chief Political Commentator of the Observer