BRITAIN'S coronavirus lockdown could last until the end of May - with the pandemic levelling out in the next ten days, a senior adviser said today.
But Professor Neil Ferguson warned a high level of infection will last for "weeks" if Brits break social distancing rules this weekend.
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The PM's adviser told BBC Radio 4 the pandemic was expected to plateau in the next week to ten days - but said people's behaviour was critical in determining what happens next.
Asked what would happen if Brits flout the social distancing rules this weekend during a mini heatwave, he said: "That moves us to a slightly more pessimistic scenario.
"We still think things will plateau but we'll be at quite high levels of infection for weeks and weeks rather than seeing quite a rapid decline as the type seen in China."
Professor Ferguson also said he was "hopeful" the drastic lockdown measures could be relaxed in a few weeks' time to make way for rapid access to testing.
But he warned the new "regime" would still "not be normal life" and would only work once positive cases are lower.
Prof Ferguson added: "We want to move to a situation where at least by the end of May that we're able to substitute some less intensive measures, more based on technology and testing, for the complete lockdown we have now."
He said if there was a rapid decline in cases, the Government would consider whether it could relax certain measures in "a way which is safe and still ensures the epidemic goes down".
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Prof Ferguson was behind Boris Johnson's decision to trigger coronavirus lockdown - warning if we didn't ramp up the fight against the killer bug, 260,000 would die.
A team from Imperial College London - led by the academic - found the new tighter controls could limit deaths to around 20,000.
They admitted the best case scenario would still see tens of thousands die.
Prof Ferguson ended up having to self-isolate himself after he fell ill with a fever - one of the main Covid-19 symptoms.
It comes as another of Boris' advisers called for Brits to catch coronavirus as lockdown will cause more harm than the killer bug.
Professor Graham Medley, the government’s chief pandemic modeller, has said the UK needs to reconsider the controversial herd immunity policy.
The adviser also warned Britain needs to consider a trade-off between the young and the old, reports.
Professor Medley claims catching the deadly disease could be the key to beating the pandemic - rather than letting letting unemployment, domestic violence and mental ill health mount up under lockdown.
He told the newspaper: "This disease is so nasty that we had to suppress it completely.
"Then we’ve kind of painted ourselves into a corner, because then the question will be what do we do now? We will have done three weeks of this lockdown so there’s a big decision coming up on April 13. In broad terms are we going to continue to harm children to protect vulnerable people, or not?”
The professor of infectious disease modelling at the London School of Hygiene and Tropical Medicine said the UK should revisit the idea of herd immunity.
When the outbreak first began to grip Britain, it was suggested one way of beating the virus was to allow 60 per cent of people to get infected.
Herd immunity is when enough people become resistant to a disease that it can no longer spread among the rest of the population.
But the strategy was abandoned by the government after its scientific advisers said this would put the NHS under immense strain with critically ill patients.
Professor Medley - a member of the government’s Scientific Advisory Group for Emergencies (Sage) - believes letting people return to work or reopening schools after lockdown will cause cases to spike.
He added: "The measures to control [the disease] cause harm.
"If we carry on with lockdown it buys us more time, we can get more thought put into it, but it doesn’t resolve anything — it’s a placeholder.”
It comes as the UK death toll yesterday overtook China and Iran's official tallies after 684 more people died.
Based on figures released by both countries' governments, Britain's total death toll of 3,645 is now 319 higher than China where the outbreak started.
And the latest deaths put Britain higher than Iran's official death toll of 3,294.
The figures for both countries have been posted on the John Hopkins University website but their governments have been accused of hiding the true numbers of deaths.
The UK's peak is now expected to hit on Easter Sunday with around 1,000 deaths a day, Health Secretary Matt Hancock has warned.
Positive cases for the deadly disease in the UK have jumped to 38,168 - up 4,450 from yesterday's total of 33,718.
Boris Johnson has urged Brits to not go out and enjoy the sunshine this weekend as he revealed he was staying in isolation because he is still sick with coronavirus.
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Britain is set for a mini April heatwave with temperatures up to 20C.
But Boris said: "I just want to say one crucial thing, to everybody thinking about this weekend and what may be some fine weather.
"I reckon a lot of people will be starting to think that this is all going on for quite a long time and they'd rather be getting out.
"Everyone may be getting a bit stir crazy.
"There may be a temptation to get out there and hang out and start to break the regulations.
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"I just urge you, not to do that.
"Please, please, stick with the guidance now."
The Queen has recorded a special coronavirus broadcast to the nation, which will air on Sunday night.