Covid variant threatens to delay the end of lockdown. The Scientific Advisory Group for Emergencies (Sage) is set to meet on Thursday amid rising fears the June 21 date for lockdown easing will be pushed back.Bolton was this week named the UK's "ground zero" for the B1617.2 strain which has become the dominant strain in four areas, figures show.Boris Johnson said it has become "of increasing concern" in Britain as data is set to show a worrying three fold increase in infections of the highly transmissible mutation.Experts advising the Government believe the final stage of Boris Johnson's road map out of lockdown -set for June 21 -could now be pushed back.