Not since the plague ravaged London in the 17th century have British households faced such tight restrictions on their movement with the aim of quelling an epidemic.
Boris Johnson, prime minister, summed up the overriding message as “stay at home” to save lives and ease pressure on the health service. But in practice the rules, which will be applied for at least three weeks, are slightly more complex.
When can I leave the house?
Above all the curbs aim to minimise contact between different households, while allowing some critical services and businesses to function.
There are just four reasons to leave the house, and even these trips should be kept to a minimum. People should always stand at least two metres apart.
Shopping is allowed for “basic necessities”, such as food and medicine. Exercise is permitted once a day, alone or with household members. Movement to seek medical care, or help the vulnerable, is acceptable. Those who “absolutely cannot” work from home can also travel.
There are some exceptions. Critical workers, such as teachers, nurses and transport workers, can continue to take children to school, which remain open for the duration of the restrictions. Parents who do not share the same home are also still able to move children between households.
When in doubt, the guidance is to stay at home.
What businesses need to close?
Pubs, clubs and cinemas were already closed on Friday. Those curbs are now extended to all non-essential retail stores, indoor and outdoor leisure facilities, communal facilities in parks, places of worship and hotels.
In practice it will mean that clothing and electronics can only be bought online; shops and open air markets will be closed.
All hair, beauty and nail salons will also shut.
Hotels or other establishments offering short-let accommodation can remain open — but their customers must be on the critical workers list.
What about the food and drink sector?
The basic principle is to shut any communal space, both indoors and outdoors.
So cafés, restaurants and canteens can remain open — but only for food delivery and takeaway customers. The main exceptions are prisons, military barracks and homeless shelters.
Planning restrictions have been relaxed to allow all premises — such as a pub or café — to offer hot food delivery, even without a permit. A licence is still required to sell or deliver alcohol.
Supermarkets and food shops and outdoor food markets should also remain open.
Are there other essential services?
Exceptions are made for a range of businesses that are either indispensable to health, or perform some essential functions.
This covers pharmacies, banks, dry cleaners and launderettes, hardware stores, pet shops and newsagents.
To enable the movement of key workers and other essential journeys, petrol stations, car rental outlets, bicycle shops and garages will also stay open.
Funeral services will continue, but with attendees spread out at a safe distance. Weddings, baptisms and other ceremonies are outlawed. Worshippers who want to come together should do so through online technology.
One exception could help parts of the entertainment industry. Theatres and concert halls are permitted to live stream performances “by a small group” as long as participants maintain a safe distance. Competitive contact sports are barred.
Many industries are not explicitly mentioned in the guidance. The ambiguity over construction sites has, for example, become a point of contention. While Robert Jenrick, the secretary of state for housing, tweeted to say working on site is still potentially permitted, the London mayor Sadiq Khan has considered suspending some projects.
How are these rules enforced?
By law, failure to comply with the guidance is an offence. Police and other public authorities are responsible for enforcing the restrictions. Sanctions can include prohibition notices and “unlimited fines”.
This is a big change for Britain’s liberal tradition. There is little precision about how rules would be enforced, or fines calculated. Peter Fahy, former chief constable of Greater Manchester Police, told the BBC there was “a huge amount of clarification needed”.
Public gatherings of more than two people are banned, according to the guidance. Any group will need to prove they either live in the same household, or are gathering with work colleagues for an essential purpose.
Are the rules stricter than elsewhere?
Britain has now caught up with many countries, from France and Italy to China and Spain, that moved to a full lockdown at an earlier stage.
While the principles are roughly the same, there are still considerable differences in approach from country to country.
In Belgium, for instance, households are permitted to meet one friend while taking exercise outdoors. Haircuts are also legal as long as only one client at a time is inside the salon.
Access to supermarkets is also restricted, so numbers do not exceed one person for every ten metres squared.
France and Spain, meanwhile, take a more exacting approach to regulating movement. People in France are required to fill out a form for any journey outside the home, while in Spain the authorities are increasingly demanding that anyone travelling to work show documents from their employers.
Although the initial UK restrictions are in place for three weeks, they could well be prolonged and made even more stringent should the measures fail to check the spread of the virus.
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