Boris Johnson's announcement means just under one third of people in England (30%) will be under extra restrictions from Wednesday, meaning they will have moved into the "high" or "very high" alert levels.
Here, we look at the rules that all of us will have to follow, how they differ in England, Scotland and Wales, and the specific restrictions being enforced in certain areas.
The rules for everyone differ in the United Kingdom's nations.
The tool below allows you to see what you can and can't do in England, Scotland, Wales and Northern Ireland.
You can get more information on how many people have died or tested positive where you live - and where the latest hotspots are - by tapping on the link below.