COVID infections appear to be "growing exponentially", a professor has warned as he urged the government not to repeat the mistake of acting too late to tackle the spread of the virus.
Sir Tim Gowers - whose argument against herd immunity helped trigger England's first lockdown last year - told Sky News that the recent increase in coronavirus cases "worries me".
"They seem to be multiplying by a certain fraction each day - in other words, growing exponentially," he said.
"We're still at a reasonably low base but, on the other hand, we know that there's a lag.
"Even if we were to take serious action and more social distancing action, that growth would continue for a while until the effect of that action kicked in."
Sir Tim, a world-leading mathematician at the University of Cambridge, was hailed by Dominic Cummings as "one of the smartest people on the planet" during his evidence to MPs this week.
Before England's first lockdown in March last year, the professor sent the prime minister's then-chief aide a five-page document warning of the need to "move urgently to extreme containment measures".
On Saturday, Sir Tim told Sky News that if it becomes clear that the UK's COVID-19 reproduction number "is significantly bigger than 1 then we just have to act".
It was announced yesterday that the R value in England is 1 to 1.1, up from 0.9 and 1.1 the previous week, suggesting the epidemic is growing.