Boris Johnson urges caution but experts are worried

England lifted almost all of its Covid-19 restrictions on July 19 amid a rise in cases driven by the spread of the Delta variant. Mandatory mask wearing is gone, limits on the numbers of people who can mix indoor or outdoor have ended, social distancing is limited to people who have tested positive for the virus and airports, and venues like nightclubs and sports stadiums are free to open at full capacity. CNN's Phil Black reports.