Addressing the public, Boris Johnson outlined a series of strict social measures, including the closure of non-essential shops and the banning of social gatherings, ordering members of the public to stay at home with only a few exceptions.
When can I leave my house?
The Prime Minister said that people are allowed to leave the house to carry out essential shopping, such as to buy food and medicine, but to do so "as infrequently as possible" and to use delivery services where they could.
Members of the public are also allowed to go outside to exercise once a day by themselves or with a member of their household. This could be a run, walk or cycle, but residents must stay two metres apart from anyone not from their own household.
Travelling to and from work is also permitted, but only when absolutely necessary and work cannot be done from home.
People can also leave the house to attend to medical needs or provide care for vulnerable people - and this includes going out to donate blood.
What about social gatherings?
Gatherings with more than two people in public, excluding people you live with, have been stopped, as have weddings, baptisms and other ceremonies.
Mr Johnson said these measures exclude funerals. In a public address at St Andrew's House in Edinburgh, Nicola Sturgeon confirmed that funerals would be permitted but that they should be “restricted to immediate family only”.
Which shops remain open?
To ensure compliance with the instruction to stay at home, Mr Johnson said all shops selling non-essential goods, including clothing and electronic stores, will be closed.
Libraries, playgrounds, outdoor gyms and places of worship will also be closed.
How will the lockdown be enforced?
The police now have power to enforce the new measures and will be able to disperse social gatherings.
People who do not follow the new measures will be landed with a fine of an unspecified amount.
How long will the lockdown last and when does it come into force?
The lockdown is to last an initial three weeks beyond which the government may relax the measures “if the evidence shows we are able to”.
It came into force at 12am on Tuesday 24 March.
Coronavirus: the facts
What is coronavirus?
COVID-19 is a respiratory illness that can affect lungs and airways. It is caused by a virus called coronavirus.
What caused coronavirus?
The outbreak started in Wuhan in China in December 2019 and it is thought that the virus, like others of its kind, has come from animals.
How is it spread?
As this is such a new illness, experts still aren’t sure how it is spread. But, similar viruses are spread in cough droplets. Therefore, covering your nose and mouth when sneezing and coughing, and disposing of used tissues straight away is advised. Viruses like coronavirus cannot live outside the body for very long.
What are the symptoms?
The NHS states that the symptoms are: a dry cough, high temperature and shortness of breath - but these symptoms do not necessarily mean you have the illness. Look out for flu-like symptoms, such as aches and pains, nasal congestion, runny nose and a sore throat. It’s important to remember that some people may become infected but won’t develop any symptoms or feel unwell.
What precautions can be taken?
Washing your hands with soap and water thoroughly. The NHS also advises to cover your mouth and nose with a tissue or your sleeve (not your hands) when you cough or sneeze; put used tissues in the bin immediately and try to avoid close contact with people who are unwell. Also avoiding touching eyes, nose and mouth unless your hands are clean.
What should I do if I feel unwell?
Don’t go to your GP but instead call NHS 111 or look online at the coronavirus service that can tell you if you need medical help and what to do next. https://111.nhs.uk/covid-19
When to call NHS 111
NHS 111 should be used if you feel unwell with coronavirus symptoms, have been in a country with a high risk of coronavirus in the last 14 days or if you have been in close contact with someone with the virus.
Sources: World Health Organisation and NHS