LONDON — When Prime Minister Boris Johnson last spoke to the British public about the coronavirus pandemic, four days ago, he was flanked by his chief medical and science advisers and issued a stark warning that “many more families are going to lose loved ones before their time.”

Even then, the comparatively relaxed measures Mr. Johnson announced seemed at odds with the gravity of the crisis he said was bearing down on the country. The dissonance has only deepened in the days since, as British officials have offered mixed messages about their strategy for fighting the virus and leaked details of more rigorous measures to come in a piecemeal, selective manner.

This muddled approach has left many in Britain confused, especially since France, Spain and other European countries have taken far harsher measures to shut down their countries. Britain, in the age of coronavirus, is a strangely ambivalent society: Pubs in London continued to hop on Saturday night, even as nervous shoppers crowded grocery stores on Sunday morning.

“Communications is absolutely essential to retaining the public’s trust,” said Devi Sridhar, director of the global health governance program at Edinburgh University. “It is frustrating that Westminster has been so cagey on why it is pursuing these policies and not transparent on the underlying evidence and models.”