So what exactly are the new measures? And how will they impact daily life?
What are the new rules?
From Monday, September 14, social meet-ups of more than six people will be illegal.
Currently, the lawful limit on gatherings is 30 people.
Why are they being introduced?
Chief medical officer, Professor Chris Whitty, and chief scientific adviser, Sir Patrick Vallance, have agreed that the action is needed urgently after the number of positive cases rose steeply.
The new rules follow a rise in cases from 12.5 per 100,000 people to 19.7 per 100,000 in the UK in the last week – with a particular rise in infections among young people.
Infections are most prevalent among the 19 to 21 age group, which are seeing 54 cases per 100,000 people.
The uptick suggests the national R number is now above 1 – meaning the virus is spreading exponentially.
Where will they apply?
The rules will apply across England to all ages and to indoor and outdoor gatherings.
This will include private homes, parks, pubs and restaurants and they will be applied to all ages.
Will there be any exemptions?
There will be a few scenarios where the restrictions do not apply, such as if your household or support bubble is larger than six people, or if you are gathering in a large group for the sake of work or education.
Weddings, funerals and organised team sports will also be exempt if they are conducted in a Covid-secure way.
What will the punishments be for breaking the rules?
The Government hope the new rules will make it easier for the police to break up large gatherings.
Failure to stick to the new rules could mean a £100 fine, which will double with every subsequent offence up to £3,200.
What has the Prime Minister said?
Mr Johnson said the Government had been forced to act because some people had failed to follow social distancing guidelines.
He told the Downing Street press conference: “With the best will in the world people have not, I’m afraid, been totally following the guidelines”.
“I certainly don’t want to blame people but now is the time for us to focus, to concentrate and to enforce the rule of six.”
Mr Johnson added that the new rules were being introduced to “prevent another wholesale national lockdown”.
Striking an optimistic note, he said he is “still hopeful” that “we could be able to get some aspects of our lives back to normal by Christmas”.
What are the enforcement measures?
Venues where people gather will now be “legally required” to get and keep the contact details of a member of every group for 21 days in order to provide them to NHS test and trace “without delay” if needed.
The hospitality venue could face a fine if it fails to stick to the Covid-security standards and the government pledged to back local authorities to make “further and faster use of their powers” against venues who break the rules.
Covid-secure marshals are to be introduced to help ensure social distancing in town and city centres. A register of environmental health officers is also to be set up to help local authorities.
Border force will step up enforcement of quarantine for travellers into the country.
Mr Johnson said there will also be a restriction of opening hours of premises in “some local areas”.
Questions remain on the specifics of the measures, but further guidance is expected to be issued by the Government.
Could the rules get stricter?
Yes, according to one of the UK’s top epidemiologists – but it all depends on the progress of the virus in the weeks and months to come.
Professor Neil Ferguson, a key figure in the early stages of the UK’s response to the virus who stopped advising the Government after it was revealed he had broken lockdown, said he was “encouraged” that ministers were now taking decisions more quickly than in spring.
“One of the mistakes made early on in this crisis was being cautious in responding to the epidemic and that led to the UK being later than we would have liked in locking down, and therefore we saw the death toll this country did see,” he told BBC Radio 4’s Today programme.
“And I am encouraged that now we are responding in a more timely manner – we have a lot more data available to track the epidemic.”
Professor Ferguson said “all the analysis” suggested there would be an “uptick in deaths in the coming weeks, so now is the time to respond” and see how much it will flatten the curve.
“And then if that is not sufficient to bring the reproduction number below one, so the epidemic starts shrinking again, then yes, we may need to clamp down in other areas,” he said.
And people should also “hesitate” at the “headlong rush to get everybody back into offices”, the Imperial College Professor said.
“The case number increases we’ve seen in the last two weeks, do not yet account for the reopening of schools. So undoubtedly that may increase transmission still further and there may be a need therefore to reduce contacts in other settings,” he added.
Professor Ferguson’s warning came as health minister Lord Bethell urged young people heading to universities across Britain to take “responsibility” in their social life for not fuelling the surging number of coronavirus cases.
Universities are already bringing in a range of measures to make campuses Covid secure, including holding many lectures online, staggering student arrival times and telling students living in halls of residence or in houses in multiple occupation who develop Covid symptoms to self-isolate in their current accommodation, rather than go home.
But with cases rising sharply among young people, Lord Bethell stressed: “We are deeply concerned about the spread among students. Some of that spread will take place in universities, and I pay tribute to the efforts of vice-chancellors to put in place social distancing arrangements in universities; we hope that they will have an impact.
“However, some of the effect is in their social life — in pubs, clubs and bedrooms up and down the country.
“That is the responsibility of the students themselves, and we are looking at measures to enhance and enforce the social-distancing measures that will stop the spread of this disease.”
What are the rules in other parts of the UK?
First Minister Nicola Sturgeon has said she cannot rule out changing the number of people allowed to gather together in Scotland as the average number of daily positive cases has trebled in three weeks.
A maximum of eight people from three households can currently meet indoors in Scotland, except in areas subject to tighter restrictions, while up to 15 people from five households can meet outside.
In Wales, up to 30 people can meet outdoors and in Northern Ireland the number is 15.