Later that evening he told Norwegian TV's leading weekly debate programme that the models run by his colleagues at the Public Health Agency of Sweden indicated that the population in Stockholm, the centre of Sweden's epidemic, could achieve herd immunity as early as next month.

"According to our modellers, we are starting to see so many immune people in the population in Stockholm that it is starting to have an effect on the spread of the infection," he said.

"Our models point to some time in May," he added, when asked about herd immunity in the capital. "These are mathematical models, they're only as good as the data we put into them. We will see if they are right."

One of the advantages of her immunity and loose social restrictions is protecting the economy.

But while Sweden has stopped short of forcing the closure of restaurants and bars, card data from Swedbank to be released on Monday shows a "sharp drop in activity in the first two weeks of April", with restaurants particularly affected, according to Andreas Wallström, the bank's chief economist.

IMF forecasts this week also predicted GDP would shrink by 6.8 per cent, broadly in line with other more restrictive countries around the continent.

Mr Tegnell's upbeat assessment came on a day when the number of recorded deaths from coronavirus in Sweden rose 130 in a single day to 1,333. By Friday the death toll had hit 1,400. Sweden's death rate is much higher than in its Nordic neighbours, but it remains comfortably better off than much more locked-down countries such as the UK and France.

Lena Einhorn, the virologist who is one of the few public critics of Sweden's strategy, told the Sunday Telegraph she was incredulous that Dr Tegnell could present this week's dismal figures as good news.

"In Finland on Thursday the cumulative number was 13 dead per million inhabitants, in Sweden it was 130 per million inhabitants. Finland: 75 dead, Norway: 152 dead, Sweden: 1,333 dead," she said. "And yet Anders Tegnell is saying 'we are feeling very hopeful'. What are they hopeful about?".

Even without being ordered into lockdown, Swedes have nonetheless been practising social distancing. Neighbouring countries like Norway and Denmark began lifting social restrictions this week, bringing much of Scandinavia broadly back in line with Sweden.

Einhorn was one of 22 scientists who in a letter published in the Dagens Nyheter newspaper on Tuesday called for Sweden's government to break urgently with the country's tradition of leaving decisions to expert agencies, seize control of coronavirus strategy from Dr Tegnell and the agency's chief Johan Carlson, and impose a similar lockdown to those seen in Finland, Norway and Denmark.

But although the group included some of the country's most eminent epidemiologists, including several with senior positions its elite Karolinska Institutet medical university, their call has backfired.

Media commentators rounded on them, with one accusing them of "behaving like scandal-mongers". None of the leaders of Sweden's opposition parties has risked criticising the Public Health Agency, or attacking the country's overall strategy.

It is too early to tell whether Sweden's gamble will pay off, but the country, it seems, is doubling down.

Here's what our readers said:

@John Hunt

"If Sweden has a population the same size as the UK, it would be on just over 10.5k deaths now. The difference is that our population density is ten times higher in the UK. For them, herd immunity really is making sense. These factors are too much for most reporters to factor in though, and the Boris bashing continues."

@Stephen Daniel

"Good on the swedes for keeping their cool and devising a strategy that suits their country (low population density, good air quality etc). Every country is different.

"One thing also to note is that in Swede 'going out' isn’t a euphemism for 'off your head on drugs and booze'."

@Peter Realistic

"Herd immunity is an iffy scenario to base your strategy on, especially as the WHO is now thinking that having had the virus only 20% may be immune from catching it again. Interesting to watch how all these countries have a different emphasis on the way out of this pandemic, no one can say who is right or who is wrong yet, and I don't think the answer to that will be in the near future.

"Countries with a lower infection rate and lower death rate initially may continue with the infection for much longer than those countries hit hard quickly. We will see."

@defacto defacto

"We need to get real. You can only achieve herd/individual immunity when you can prove that nobody can be re-infected by the virus. At the moment, all we and other countries can do is hope that the existence of anti-bodies = immunity. Until we get a vaccine, we are walking in the dark. Without torches."

@Dave Andrews

"If herd immunity can't be achieved with this virus surely that doesn't bode well for the hope of a vaccine in the near future? Isn't the protective mechanism of an initial actual infection and administration of a vaccine based on the stimulation of an immune response in both scenarios?