London and Essex are among the areas moving into second tier coronavirus restrictions from Saturday. It means millions more people won't be able to mix with other households indoors.
The announcement follows the introduction of England's new three-tier system. Other parts of the UK have also introduced new restrictions.
How does England's new three-tier system work?
Every area of England now falls into three categories - medium (Tier 1), high (Tier 2) or very high (Tier 3), depending on the local rate of infection.
What are the rules for Tier 1 (medium alert)?
Areas in Tier 1 are subject to the basic national rules previously in force.
You may not meet in a group of more than six people, indoors or outdoors, unless you're in a larger household or a support bubble.
Pubs, bars and restaurants in a Tier 1 area must close by 22:00.
What are the rules for Tier 2 (high alert)?
The rules for Tier 1 also apply in Tier 2.
In addition, you are not allowed to meet socially with people you do not live with indoors - this includes private homes, as well as pubs or restaurants.
People in support bubbles can go on meeting as before and informal childcare may also be provided.
You can still meet friends and family outdoors, but only in a group of up to six people.
The areas to go into high alert restrictions this weekend are:
Elmbridge in Surrey
Barrow in Furness, Cumbria
North East Derbyshire
What are the rules in Tier 3 (very high alert)?
Areas with the most rapidly rising transmission rates are placed in Tier 3.
You are not allowed to meet socially with anybody who is not part of your household or your support bubble indoors or in certain outdoor locations.
You cannot meet in private gardens or pub gardens, but can meet in parks, beaches, countryside or forests, as long as you are not in a group of more than six.
Pubs and bars must close unless they are serving substantial meals - alcohol can only be served as part of a meal.
People are being advised not to travel into or out of Tier 3 areas, other than for work, education, youth services or because of caring responsibilities.
At present, only the Liverpool City Region is classed as very high risk. A final decision on whether to add Greater Manchester has not been made.