I was wrong. Or I think I was. I heard Boris Johnson on 3 March leap into war mode and publish 28 pages of emergency plans, should coronavirus take hold in Britain. There were reports that “half a million could die”. I was sceptical.

I noted that in 1999 it had been said that BSE “could kill” half a million. Sars in 2003 had a “25% chance of killing tens of millions”. In 2009, the British government said 65,000 “could die” of swine flu.

What was different this time? The experience of China through January was enough to put other countries on guard. A widely publicised study of the virus in the January Lancet by the University of Hong Kong professor Joseph Wu and his team warned the world that a global outbreak “could become inevitable because of substantial exportation of presymptomatic cases”. It called on all health authorities to prepare.

We now know that governments round the world reacted very differently. Korea and Taiwan threw resources at testing, tracing and quarantining. In Europe, so did Germany and Sweden. Italy imposed increasingly severe lockdowns, followed by France, Denmark and Norway. The US did almost nothing; Russia and many African nations likewise. Everywhere people were told to “listen to the science”.

At first, the British government clearly did not take the virus seriously – despite Johnson’s 3 March clarion call. While the Koreans were installing drive-through testing booths and Poles were taking temperatures in airports, Johnson was joking about handwashing.

The policy was apparently to assume that, like previous scares, Covid-19 would pass. The first intimation that Britain was getting serious came with Johnson’s daily press conferences from 16 March, flanked for protection by his chief scientific adviser, Sir Patrick Vallance, and chief medical officer, Chris Whitty. The policy was containment and mitigation. The sick would be treated. Crowds should be avoided. “Herd immunity” should rise to 60 or 70% and time would do the rest. The Swedish government made roughly the same announcements. At the time I found this approach plausible.

Across Europe that week, pandemonium broke out. Deaths were rising in Italy and Spain. Lockdown was instituted on all sides. Ministers were clearly panicked by a report from Imperial College London under Prof Neil Ferguson, the most alarming document I have read outside the realm of nuclear war planning. In a welter of graphs and statistics, it rubbished the government’s mitigation strategy and advised full-scale “suppression”. Even if the virus was suppressed, the report warned it could return and would be as bad or even worse. The report estimated that deaths could range from 20,000 in the best-case scenario to the familiar half-million in the worst.

On 23 March a clearly traumatised Johnson appeared alone on television, unattended by scientists and with a union jack behind him. He and his in-house scientists fell into line with Imperial’s projections. Schools should close, everyone should stay at home and he would bring in emergency powers with fines. In ham-Churchillian, he told Britons to show a “national spirit as they have done before” and come together – or rather stay apart.

But “the science” appeared to lead us to differing conclusions. The same weekend Johnson did his volte face, an Oxford University team led by Sunetra Gupta, a professor of theoretical epidemiology, pointed out that figures on the morbidity of Covid-19 were virtually meaningless in the absence of testing. They suggested that half the population could have had already it mildly, which, if true, would imply the death rate was far lower than thought. Were that the case, it might seem more sensible to throw resources at the NHS and merely encourage people to avoid crowds rather than shut down the economy.

Connoisseurs of academic backbiting can enjoy the eight scientists contacted by the Science Media Centre, who rubbished the Oxford study, though some carefully hedged their bets.

But Gupta was not alone. The maverick – but frequently accurate – pandemic forecaster at Stanford University John Ioannidis called the data collected so far on the pandemic “utterly unreliable”. It would one day, he claimed, be regarded as “an evidence fiasco”. He pointed out that the Covid-19 hothouse of the Diamond Princess cruise ship yielded a mortality rate of 1% in a population largely composed of high-risk older people. He suggested the US would end up with an annual rate possibly as low as 0.05% (seasonal flu is around 0.1%). The Swedish government took a similar view.

The Cambridge University statistician David Spiegelhalter was almost as sanguine on the BBC’s More or Less programme. He did not challenge the disease’s virulence but suggested it might compress the annual flu death rate into a few weeks – putting intense pressure on hospitals – with the only “extras” coming from non-vulnerable groups. Yet more scepticism was expressed by a former NHS pathologist, John Lee, who suggested deaths of elderly people were being very differently recorded in different countries. How many were really dying “of” Covid-19 rather than of something else “with” it?

Science was plainly suffering herd disagreement – leaving politicians floundering. There is clearly more than one side to this argument. Will Sweden prove better or worse than adjacent Denmark? One day the mother of all inquiries will tell us. For the present, all we know is that the world is conducting a massive real-time experiment in state authority.

The world is not divided between “the science”’ and other mortals. Scientists are like the rest of us. They form assumptions and grasp at evidence to validate them. They are optimists or pessimists, by nature risk-taking or cautious. My wife and I share inputs, hear the same news and read the same papers. But I am an optimist and she is a pessimist. I think we could have stuck to the Swedish model. I think the crisis will be over in three weeks. She believes it will last months. It is not much comfort that we both have scientists on our side.

• Simon Jenkins is a Guardian columnist





