Johnson has announced more easing of restrictions, with people urged to return to public transit and workplaces. He says sports fans should return to stadiums by October and remaining restrictions could be lifted from November, "possibly in time for Christmas."
But epidemiologist John Edmunds, a member of the government's Scientific Advisory Group for Emergencies, says a return to pre-pandemic normality wouldn't be possible until there's a vaccine for the virus.
He says a world where people can "go to work normally, travel on the buses and trains, go on holiday without restrictions, meet friends, shake hands, hug each other and so on -- that's a long way off, unfortunately."
England's Chief Medical Officer, Chris Whitty, also says social distancing rules would have to be in place for a "prolonged period."
Britain has registered more than 45,000 confirmed COVID-19 deaths, the highest total in Europe.