He added that the restrictions remained "under constant review" and would be checked again in three weeks and they would be relaxed "if the evidence shows we are able to".
From this evening people must stay at home except for shopping for basic necessities, daily exercise, any medical need and travelling to and from essential work.
"Shopping for basic necessities, as infrequently as possible one form of exercise a day, for example a run, walk, or cycle alone or with members of your household; any medical need, to provide care or to help a vulnerable person, and travelling to and from work, but only where this is absolutely necessary and can not be done from home".
"The way ahead is hard, and it is true that many lives will sadly be lost", Johnson said.
Parks would stay open for train however gatherings could be dispersed, Johnson mentioned.
Responding to the statement by the Prime Minister, Labour leader Jeremy Corbyn commented: "The Prime Minister is right to call for people to stay at home, protect our NHS and save lives".
The Prime Minister announced that the government would "immediately close all shops selling non-essential goods, including clothing and electronic stores and other premises including libraries, playgrounds and outdoor gyms, and places of worship". On Monday morning, the London Underground was packed with rush hour crowds flouting the advice to stay home.
Weddings and baptisms and other ceremonies will also be stopped, but funerals will continue.
But during the weekend, large groups of people were seen in some parks and tourist spots, prompting concerns that many people might be ignoring government's advice of avoiding social contact.
All however important outlets must shut instantly and other people ought to now not meet household or mates or danger being fined, Johnson mentioned in a televised deal with to the nation.
Death cases have reached 335. But for some older adults and people with existing health problems, it can cause more severe illness, including pneumonia.
"But only when this is absolutely necessary", Johnson said, "and can not be done from home". "And yet it is also true that there is a clear way through...."
In an address last night, the Prime Minister declared the coronavirus a "moment of national emergency".