A new national lockdown across England means people must stay at home unless for specific reasons, such as attending school or college, or going to the supermarket.
He said the measures were necessary to avert bleak predictions of 85,000 deaths this winter.
Below, MailOnline outlines the key details of the new restrictions, which will see pubs, bars and restaurants forced to close once again.
Prime Minister Boris Johnson announced new lockdown measures at Downing Street press conference on Saturday
When do the new rules come into force?
The new national lockdown will run from Thursday November 5 until Wednesday December 2.
The lockdown will then be eased on a regional basis according to the latest coronavirus case data at that time.
Can I leave my home?
Yes but only for specific reasons such as education, work if you cannot work from home and for exercise, which you can take as many times a day as you wish.
Construction sites or manufacturing facilities are examples of workplaces which employees will still need to go to.
People can also leave home for recreation with their own household, or on their own with one person from another household (a 'one plus one' rule).
Examples of recreation include meeting up with a friend in the park for a walk or to sit on a bench and eat a sandwich.
People will not be allowed to meet in homes and gardens, and golf clubs will remain shut.
People can also leave home to shop for food and essentials and to provide care for vulnerable people or as a volunteer.
Attending medical appointments is also allowed or to escape injury or harm (such as for people suffering domestic abuse).
Support bubbles will remain in place and people can still meet up in their bubble.
Children can move between the homes of their parents if their parents are separated.
What will close?
Non-essential shops, leisure and entertainment venues will all be closed.
Click and collect can continue and essential shops such as supermarkets will remain open.
Bars, pubs and restaurants must stay closed except for delivery or take-away services.
Hairdressers and beauty salons will close.
Non-essential shops, leisure and entertainment venues will all be closed
What if I shielded last time?
Prime Minister Boris Johnson said people over 60 and those who are clinically vulnerable are being told to be especially careful to follow the rules and minimise their contact with others.
Anyone who was formally notified that they should shield last time and not go out to work will be advised not to go out to work this time.
However, formal shielding as happened during the March and April lockdown - where people were told not to leave home for any reason - will not be brought in.
Prime Minister Boris Johnson said people over 60 and those who are clinically vulnerable are being told to be especially careful to follow the rules and minimise their contact with others
Should my children go to school or to the childminder? Can they go to a playground?
Yes, schools, colleges and universities will all remain open.
Childminders and nurseries will stay open and childcare bubbles, where for example a grandparent provides childcare while a parent works, will be able to continue.
After-school clubs and sports clubs will be suspended until December 2.
Playgrounds and parks will remain open.
Schools, colleges and universities will all remain open. Childminders and nurseries will stay open and childcare bubbles, where for example a grandparent provides childcare while a parent works, will be able to continue.
Can I go on holiday?
No, you are advised not to travel unless for essential reasons. People can travel for work.
Those who are already on holiday will be able to return to the UK and airports and train stations will remain open.
What if I'm already abroad?
Travellers are not required to return from their trips early.
Airlines are responsible under consumer law to bring travellers home, but flight schedules will be slashed in response to the drop in demand, meaning many people will be forced to change their travel dates.
You are advised not to travel unless for essential reasons. People can travel for work
I thought we could go to the Canary Islands?
It is less than two weeks since the Government removed the quarantine requirement for people returning from the Spanish islands.
This led to airlines putting on extra flights to cope with the surge in bookings.
Will travel corridors continue?
The Prime Minister did not mention travel corridors in his Saturday night press conference, meaning people arriving from some areas are likely to continue being exempt from quarantine.
But the lockdown means the number of travellers will be diminished anyway.
Will I get my money back if I've booked a holiday I can no longer go on?
If your flight is still going ahead and nothing has changed in your destination, you are not automatically entitled to a refund.
But many aircraft are likely to be grounded from Thursday due to the new restrictions, meaning people with existing bookings will be due a refund.
If I am entitled to a refund, how quickly will I get my cash?
UK consumers are protected under European laws which state that they should receive full cash refunds within seven days for cancelled flights and 14 days for package holidays that do not take place.
But since the coronavirus outbreak many people have faced difficulties obtaining payouts from airlines and holiday firms.
That situation is likely to continue over the coming weeks.
Is there a furlough scheme?
Yes, furlough will be payable at 80 per cent for the duration of the package of tougher national measures.
The support will be available across the UK.
Business premises forced to close in England will also receive grants worth up to £3,000 per month under a Local Restrictions Support Grant.
A further £1.1 billion will be given to local authorities - distributed on the basis of £20 per head - for one-off payments to support businesses.
Is there support for mortgages?
Yes. Homeowners will be able to take the option of mortgage payment holidays, which had been due to end on Saturday but have been extended.
Can I go to church?
Churches will remain open for private prayer.
Funerals are limited to close family members only. It is currently unclear what the rules are for weddings.
Churches will remain open for private prayer. Funerals are limited to close family members only. It is currently unclear what the rules are for weddings. Pictured: St Bartholomew The Great church in Smithfield, London
Will Premier League football matches continue?
Yes. Boris Johnson said games would continue despite the restrictions.
What if I live in an area with lower cases?
You must still observe the rules because they apply across England.
Professor Chris Whitty said that many of the areas with lower case numbers have the highest rates of increase.
He also warned: 'Some areas including the South West are likely to get pressure on beds really relatively early because of the way the NHS is constructed in those areas.'