British Prime Minister Boris Johnson told people on Tuesday to work from home where possible and ordered bars and restaurants to close early to tackle a fast-spreading second wave of COVID-19 with restrictions lasting probably six months.
Here are some details about the new measures in England, which are likely to be mirrored for the most part in Scotland, Wales and Northern Ireland.
VENUES TO CLOSE AT 10 P.M.
From Thursday, hospitality venues like pubs and restaurants must close at 10 p.m.
WORK FROM HOME
Workers should work from home if they can, but those who can not should continue to attend their workplaces.
FINES FOR BUSINESSES
Businesses breaking COVID rules could be fined up to 10,000 pounds ($12,800), matching a penalty for individuals who breach self-isolation rules.
MANDATORY FACE MASKS
Face masks will now be mandatory for retail workers and users of taxis. Hospitality staff and their customers will also need to wear masks - unless seated at a table to eat or drink.
COVID GUIDELINES FOR RETAIL, LEISURE TO BECOME ENFORCEABLE
COVID guidelines for the retail, leisure and tourism sectors will become legal obligations - meaning companies could be fined or closed if they break the rules.
FINES FOR THE PUBLIC
The penalty for failing to wear a mask - or breaking the rule that limits gatherings to six people - will be doubled to 200 pounds for a first offence.
WEDDINGS AND FUNERALS
From Monday, a maximum of 15 people will be able to attend wedding ceremonies and receptions. Up to 30 will still be able to attend a funeral.
NO CROWDS FOR SPORTING EVENTS, BUSINESS CONFERENCES
The plan to reopen large sporting events and business conferences from Oct. 1 will no longer take effect.
MORE POLICE, MAYBE MILITARY
More funding will be given to police to help enforce the new rules. Johnson said the military could be called upon to help free up the police.
Johnson said the government reserved the right to ratchet up the restrictions if these measures do not calm the pandemic.