Stark analysis that warned the UK government’s strategy would see the NHS overwhelmed and lead to 250,000 deaths helped prompt yesterday’s drastic escalation of the Covid-19 response.

Researchers said harsh social restrictions until a vaccine is ready – which could be over 18 months away – were the only way to push the number of cases down to a level that the health service can cope with.

They warn ‘no public health intervention with such disruptive effects on society has been previously attempted for such a long duration of time.’

They cautioned the existing tactic of mitigating the worst health effects of the virus but not trying to stop it spreading would see all the UK’s intensive care beds filled at least eight times over and see a quarter of a million people die.

Scotland’s chief medical officer yesterday called on people to avoid unnecessary social contact to “prevent the NHS being overwhelmed”. At the same time, Nicola Sturgeon said the number of cases in Scotland was likely to start doubling every five days.

The report, produced by a team at Imperial College London, says their calculations have ‘informed policymaking in the UK and other countries in recent weeks.’

It considers two basic responses to the virus – mitigating its worst effects or trying to stop it spreading through reducing non-essential contact.

A ‘minimal’ level of suppression would involve the entire population limiting their social interactions, and people and their family members staying at home if they have the virus.

Researchers say university and school closures could follow, and the whole package will need to be maintained until a vaccine becomes available.

Key calculations relating to how many people will need hospital treatment have shifted in recent days, the report states, based on evidence from Italy.

They currently believe 27% of over 80s with the virus will need to go into hospital, seven in ten of which in critical care.

The mortality rate for this age group is thought to be 9% but this decreases rapidly by age and is less than 1% for under 60s.