Government sources said the lockdown in the north of England (see video above) had been driven by a failure to adhere to social distancing within the home and within “loosely defined” households across large extended families.
On Friday night, one senior health official said Prof Whitty did not feel it was his job to determine which sacrifices lay ahead – that would be for ministers.
But in making such a detailed public statement, the chief medical officer has turned all eyes to Mr Johnson as he considers Britain’s precarious position.
A source close to Prof Whitty said: “Chris feels you can’t have any further easements of lockdown now without pulling back on something else.
“Clearly, schools are a priority. But as far as he’s concerned, it’s not for him to decide what measures you reintroduce to allow that to happen – that one is down to ministers.
“But he feels very strongly that you cannot make any more relaxations now unless you tighten up another measure to compensate.”
One health official said on Friday that the deteriorating situation could see pubs closed in some areas in order to reduce transmission rates and make it safer for schools to reopen. He said ministers were reluctant to make “blanket” moves to reverse recent relaxations but could not rule it out.
If rates of infection continue to rise, measures are likely to focus first on local restrictions. These could see closures of pubs, restaurants or workplaces if surveillance data links them to outbreaks.
“This is really led by the data,” the health official said. “If cases are being fuelled by transmission between households in one part of the country, that’s what will be targeted.
“If in another part of the country it’s about pubs not enforcing social distancing, then they could be closed, or particular workplaces can be closed, or we could see moves like those in the north-west happening elsewhere.
“There is a real reluctance to introduce blanket bans across the country, to penalise people in the south-west and stop them going to the pub because people in the north-east are mixing within households.”
Above all this hangs the hope that fear of losing recently won freedoms will be enough to improve compliance with current rules on social distancing so that infection rates fall.
On Friday, Boris Johnson said: “At this stage, we are not changing the rules on social contact nationally. I don’t want to tell people to spend less time with their friends – but unless people follow the rules and behave safely, we may need to go further.”