A vast numbers of businesses including pubs, restaurants, and hotels can reopen from tomorrow, and restrictions will also loosen on how many people could meet at one time, both indoors and outside.
But Chief Medical Officer Professor Chris Whitty said a second wave was a “real possibility”, and added: “If individuals, families and firms do not take them seriously the possibility of a second wave goes up sharply.”
Mr Johnson said the Government has “all sorts of measures in reserve” in the event of a second wave of Covid-19 infections.
The comments, made in a Downing Street press briefing today, came as Yorkshire recorded no new coronavirus deaths yesterday, leaving the total number of people who have died in the region after testing positive for the disease at 2,840.
Nationally, however, a further 137 deaths were recorded, bringing the total to 44,131.
The growth rate of the virus - how quickly the number of infections is changing day by day and, as the number of infections decreases - had also risen to between minus six per cent and zero per cent per day compared with a rate of minus four per cent to minus two per cent per day last week.
If the growth rate is greater than zero, and therefore positive, then the disease will grow.
If the growth rate is less than zero, then the disease will shrink.
Mr Johnson said: “My view, my urging to everybody, can be summed up in the phrase ‘enjoy summer safely’.
“I do want people to feel that it’s safe to go and enjoy themselves and enjoy hospitality.
“But it’s got to be done in a responsible way.”
Mr Johnson said that if people gave their names behind the bar or in restaurants and observed social distancing and hand hygiene then it would be a success.
The Government’s chief scientific adviser Sir Patrick Vallance said social distances should be enough to keep the pandemic under control but warned “we will see local outbreaks”.
“We need to make sure as winter comes, which is the big risk, that we are prepared to be able to deal with it,” Sir Patrick said.
On easing lockdown restrictions, Prof Whitty said: “None of us believe, and I am sure nobody watching this believes, this is a risk-free next step.
“It is absolutely not, and that’s why we have to be really serious about it.”
Mr Johnson refused to comment on his father Stanley reportedly flying to Greece in apparent breach of Foreign Office guidance to avoid non-essential travel.
When asked why the public should obey all the rules when his father and top aide Dominic Cummings had not done so, he said: “Durham Police made it clear they were not pursuing that.
“I make it a normal practice not to comment on the movements and doings of my family.
“When you look at what the British public have done over the last three months it has been a phenomenal effort to follow the guidance and get this thing under control. People have worked together and done an absolutely heroic job. We have got to keep that going now.”
He added: “This is a big turning point for us, we’ve got to get it right.”