Sir Jeremy Farrar, a member of the Government's Scientific Advisory Group for Emergencies (Sage), said coronavirus transmission in secondary schools is “high”. He added that the new lockdown - which runs from Thursday until December 2 - may need to be looked at again in four weeks if the R value remains above one.
Sir Jeremy told the BBC's Andrew Marr Show: "The big difference to the first lockdown is that schools remain open.
"Because we have delayed the onset of this lockdown it does make keeping schools open harder.
"We know that transmission, particularly in secondary schools is high.
"Personally I think this is definitely the lockdown to put in place now but if that transmission, particularly in secondary schools, continues to rise then that may have to be revisited in the next four weeks in order to get R below one and the epidemic shrinking."
An expert has warned England’s second national lockdown may not be as effective as the first (Image: PA)
Prime Minister Boris Johnson on Saturday announced a second national lockdown in England (Image: PA)
Former chief scientific adviser Sir Mark Walport echoed Sir Jeremy’s comments.
Sir Mark said the latest restrictions were not as "severe" as the first lockdown ordered in March.
He added that there was a "possibility" the restrictions may be needed for more than four weeks.
He told Sky’s Sophy Ridge On Sunday: "It's unlikely this time to come down quite as fast as it did during the first lockdown because we have got schools open."
READ MORE: Second coronavirus lockdown sparks fears of economic MELTDOWN
Unlike the first lockdown earlier this