When Britain was being locked down, the country was assured that all risks had been properly and robustly considered. Yes, schools would close and education would suffer. Normal healthcare would take a hit and people would die as a result. But the government repeatedly said the experts had looked at all this. After all, it wasn’t as if they would lock us down without seriously weighing up the consequences, was it?

Those consequences are still making themselves known: exams madness, the NHS waiting list surge, thousands of unexplained ‘excess deaths’, judicial backlogs and economic chaos. Was all that expected, factored in, and thought by leaders to be a price worth paying? Right at the start of lockdown, ministers had already started to worry that the policy was being recklessly implemented without anyone thinking about the side-effects. Only a handful of key players at the very top made the decisions: among them Rishi Sunak, the chancellor. He has now decided to go public on what happened.

When we meet at the office he has rented for his leadership campaign, soon to enter its final week, he says at the outset that he’s not interested in pointing the finger at the fiercest proponents of lockdown. No one knew anything at the start, he says: lockdown was, by necessity, a gamble. Chris Whitty and Patrick Vallance, the chief medical officer and chief scientific adviser, would openly admit that lockdown could do more harm than good. But when the evidence started to roll in, a strange silence grew in government: dissenting voices were filtered out and a see-no-evil policy was applied.

Sunak’s story starts with the first Covid meeting, where ministers were shown an A3 poster from scientific advisers explaining the options. ‘I wish I’d kept it because it listed things that had no impact: banning live events and all that,’ he says. ‘It was saying: you should be careful not to do this stuff too early, because being able to sustain it is very hard in a modern society.’ So the scientific advice was, initially, to reject or at least delay lockdown.

This all changed when Neil Ferguson and his team at Imperial College published their famous ‘Report 9’, which argued that Covid casualties could hit 500,000 if no action was taken – but the figure could be below 20,000 if Britain locked down. That, of course, turned out to be a vast exaggeration of lockdown’s ability to curb Covid deaths. Imperial stressed it did ‘not consider the wider social and economic costs of suppression, which will be high’. But surely someone involved in making the policy would figure it out.

This was the crux: no one really did. A cost-benefit calculation – a basic requirement for pretty much every public health intervention – was never made. ‘I wasn’t allowed to talk about the trade-off,’ says Sunak. Ministers were briefed by No. 10 on how to handle questions about the side-effects of lockdown. ‘The script was not to ever acknowledge them. The script was: oh, there’s no trade-off, because doing this for our health is good for the economy.’

If frank discussion was being suppressed externally, Sunak thought it all the more important that it took place internally. But that was not his experience. ‘I felt like no one talked,’ he says. ‘We didn’t talk at all about missed [doctor’s] appointments, or the backlog building in the NHS in a massive way. That was never part of it.’ When he did try to raise concerns, he met a brick wall. ‘Those meetings were literally me around that table, just fighting. It was incredibly uncomfortable every single time.’ He recalls one meeting where he raised education. ‘I was very emotional about it. I was like: “Forget about the economy. Surely we can all agree that kids not being in school is a major nightmare” or something like that. There was a big silence afterwards. It was the first time someone had said it. I was so furious.’

One of Sunak’s big concerns was about the fear messaging, which his Treasury team worried could have long-lasting effects. ‘In every brief, we tried to say: let’s stop the “fear” narrative. It was always wrong from the beginning. I constantly said it was wrong.’ The posters showing Covid patients on ventilators, he said, were the worst. ‘It was wrong to scare people like that.’ The closest he came to defying this was in a September 2020 speech saying that it was time to learn to ‘live without fear’ – a direct response to the Cabinet Office’s messaging. ‘They were very upset about that.’

His Eat Out to Help Out campaign was designed to be an optimistic counter-narrative. ‘The survey data across Europe showed that our country was far and away the least likely to get back to normal. All the evidence was that everyone was too scared to go and do things again. We have a consumption-driven economy, so that would be very bad.’ As indeed it was. The UK ended up with the worst economic downturn in Europe.

Lockdown – closing schools and much of the economy while sending the police after people who sat on park benches – was the most draconian policy introduced in peacetime. No. 10 wanted to present it as ‘following the science’ rather than a political decision, and this had implications for the wiring of government decision-making. It meant elevating Sage, a sprawling group of scientific advisers, into a committee that had the power to decide whether the country would lock down or not. There was no socioeconomic equivalent to Sage; no forum where other questions would be asked.

So whoever wrote the minutes for the Sage meetings – condensing its discussions into guidance for government – would set the policy of the nation. No one, not even cabinet members, would know how these decisions were reached.

In the early days, Sunak had an advantage. ‘The Sage people didn’t realise for a very long time that there was a Treasury person on all their calls. A lovely lady. She was great because it meant that she was sitting there, listening to their discussions.’

It meant he was alerted early to the fact that these all-important minutes of Sage meetings often edited out dissenting voices. His mole, he says, would tell him: ‘“Well, actually, it turns out that lots of people disagreed with that conclusion”, or “Here are the reasons that they were not sure about it.” So at least I would be able to go into these meetings better armed.’

But his victories were few and far between. One, he says, came in May 2020 when the first plans were being drawn to move out of lockdown in summer. ‘There’s some language in there that you will see because I fought for it,’ he says. ‘It talked about non-Covid health impact.’ Just a few sentences, he says, but he views the fact that lockdown side-effects were recognised at all at that point as a triumph.

He doesn’t name Matt Hancock, who presided over all of this as health secretary, or Liz Truss, who was silent throughout. As he said at the outset, he doesn’t want to name names but rather to speak plainly about what the public was not told – and the process that led to this. Typically, he said, ministers would be shown Sage analysis pointing to horrifying ‘scenarios’ that would come to pass if Britain did not impose or extend lockdown. But even he, as chancellor, could not find out how these all-important scenarios had been calculated.

‘I was like: “Summarise for me the key assumptions, on one page, with a bunch of sensitivities and rationale for each one”,’ Sunak says. ‘In the first year I could never get this.’ The Treasury, he says, would never recommend policy based on unexplained modelling: he regarded this as a matter of basic competence. But for a year, UK government policy – and the fate of millions –was being decided by half-explained graphs cooked up by outside academics.

‘This is the problem,’ he says. ‘If you empower all these independent people, you’re screwed.’ Sir Gus O’Donnell, the former cabinet secretary, has suggested that Sage should have been asked to report to a higher committee, which would have considered the social and economic aspects of locking down. Sunak agrees. But having been anointed from the start, Sage retained its power until the rebellion that came last Christmas.

When the Omicron variant started to rise last December, the dance began again. A Sage analysis claimed that without a fourth lockdown, Covid deaths could hit 6,000 a day. That was out by a factor of 20. But we only know this because, for once, the government rejected Sage’s advice. This time, Sunak was taking soundings of his own – including academics at Stanford University, where he went to business school, and his former colleagues in the world of finance who had started to do some Covid modelling. Crucially, JP Morgan used South African data on Omicron to suggest that UK hospitals would not be overrun – contrary to Sage’s predictions.

‘I’m still on the JP Morgan research [email] list,’ he says. ‘It gives me a bit of a different perspective.’ In the case of Omicron, if that very different perspective was right, then every single one of the 12 Sage scenarios provided to ministers was a vast exaggeration and Britain would be locked down needlessly. Yet the wheels were already in motion, says Sunak. ‘They had briefed already that there was going to be a press conference. The system just kind of geared up.’

He flew back early from a trip to California. By this time JP Morgan’s lockdown analysis was being emailed around among cabinet ministers like a samizdat paper, and they were ready to rebel. Sunak met Johnson. ‘I just told him it’s not right: we shouldn’t do this.’ He did not threaten to resign if there was another lockdown, ‘but I used the closest formulation of words that I could’ to imply that threat. Sunak then rang around other ministers and compared notes.

Normally, cabinet members were not kept in the loop as Covid-related decisions were being made – Johnson’s No. 10 informed them after the event, rather than consulting them. Sunak says he urged the PM to pass the decision to cabinet so that his colleagues could give him political cover for rejecting the advice of Sage. ‘I remember telling him: have the cabinet meeting. You’ll see. Every-one will be completely behind you… You don’t have to worry. I will be standing next to you, as will every other member of the cabinet, bar probably Michael [Gove] and Saj [Javid].’ As it was to prove.

Is Sunak exaggerating his own role? For what it’s worth, his account squares with what I picked up from his critics in government: that the money-obsessed Sunak was on a one-man mission to torpedo lockdown. And perhaps the Prime Minister as well. ‘Everything I did was seen through the prism of: “You’re trying to be difficult, trying to be leader,”’ he says. He tried not to challenge the Prime Minister in public, or leave a paper trail. ‘I’d say a lot of stuff to him in private,’ he says. ‘There’s some written record of every-thing. In general, people leak it – and it causes problems.’

At any point, Sunak could have gone public – or even resigned. I ask him if he should have done. To quit in that way during a pandemic, he says, would have been irresponsible. And to go public, or let his misgivings become known, would have been seen as a direct attack on the PM.

At the time, No. 10’s strategy was to create the impression that lockdown was a scientifically created policy which only crackpots dared question. If word leaked that the chancellor had grave reservations, or that a basic cost-benefit analysis had never been applied, it would have been politically unhelpful for No. 10.

Only now can Sunak speak freely. He is opening up not just because he is running to be prime minister, he says, but because there are important lessons in all of this. Not who did what wrong, but how it came to pass that such important questions about lockdown’s profound knock-on effects – issues that will probably dominate politics for years to come – were never properly explored.

‘All this blaming civil servants – I hate it,’ he says, ‘We are elected to run the country, not to blame someone else. If the apparatus is not there, then we change it.’ When things go well, he says, ‘it comes from the person at the top being able to make decisions properly – and understanding how to make good decisions’.

Which is, of course, his ultimate point: ‘The leader matters. It matters who the person at the top is.’ It’s the reason he resigned, finally, and part of his pitch to be leader of the Conservative party. He says ministers need to be honest about the flip-side of any policy (including tax cuts), and that denial always makes things worse.

‘It's not a holiday, it’s a lockdown’ — Police cleared out sunbathers from this London park days after PM Boris Johnson ordered a nationwide lockdown pic.twitter.com/gswjA3lls9

And the other lessons of lockdown? ‘We shouldn’t have empowered the scientists in the way we did,’ he says. ‘And you have to acknowledge trade-offs from the beginning. If we’d done all of that, we could be in a very different place.’ How different? ‘We’d probably have made different decisions on things like schools, for example.’ Could a more frank discussion have helped Britain avoid lockdown entirely, as Sweden did? ‘I don’t know, but it could have been shorter. Different. Quicker.’

There’s one major factor he doesn’t raise: the opinion polls. Lockdowns were being imposed all over a terrified world in March 2020 and the Prime Minister was already being accused of having blood on his hands by failing to act earlier. Surely whoever was in No. 10 would have been forced to lock down by public opinion? But the public, Sunak says, was being scared witless, while being kept in the dark about lockdown’s -likely effects. ‘We helped shape that: with the fear messaging, empowering the scientists and not talking about the trade-offs.’

Those trade-offs are apparent. At first, no one asked what all those cancelled NHS appointments would mean. When the answer came, it was devastating: a waiting list that is projected to grow from six million now to nine million by 2024. Avoidable cancer deaths due to late diagnosis will run into the thousands. Then there’s the economic impact. ‘We are short of 300,000 to 400,000 [workers],’ he says. ‘That is a problem.’ Some 5.3 million are on out-of-work benefits, with many over-fifties giving up on work entirely: a tendency that Sunak says was not spotted ‘until it was too late’.

Even now, Sunak doesn’t argue that lockdown was a mistake – just that the many downsides in health, the economy and society in general could have been mitigated if they had been openly discussed. An official inquiry has begun, but Sunak says there are lessons to learn now. The emergence of another Covid variant (or another new pathogen) may lead to demands for another lockdown someday. One of the questions will be how to protect democratic scrutiny in a future crisis – how to ensure that robust questioning and testing of policy continues, even when it is expedient for the government to suppress the debate.

To Sunak, this was the problem at the heart of the government’s Covid response: a lack of candour. There was a failure to raise difficult questions about where all this might lead – and a tendency to use fear messaging to stifle debate, instead of encouraging discussion. So in a sentence, how would he have handled the pandemic differently? ‘I would just have had a more grown-up conversation with the country.’

Fraser Nelson is editor of The Spectator