Covid cases have fallen by a third in a week but Boris Johnson warned they would rise again if people did not remain cautious.
The prime minister braced the country for a further increase resulting from the end of restrictions as he cautioned against drawing “premature conclusions” that the threat of the pandemic had passed.
The sustained reduction has taken ministers and scientists by surprise, with the government concluding that much of it is likely to be real, but they are concerned that it will reverse if people react to the good news by becoming less cautious.
Cases have fallen most among those in their late teens and early twenties, according to analysis of internal government data. Some scientists believe this reflects less testing as
