Prof Whitty said the more than one million people deemed extremely clinically vulnerable must continue shielding, but offered a glimmer of hope when he said that the infection level may be sufficiently reduced to allow their freedom "relatively soon".
The PM also advised people not to meet groups of six from other households in quick succession, in order to limit the risk of transmission. It's also important to note that these rules are for England specifically, as the devolved nations have announced their own slightly different rules; Scotland, for instance, is now allowing gatherings of up to eight people from two different households.
The measure will be introduced on Monday June 1 and socially distanced meetings can take place in private gardens as well as in public outdoor spaces.
The Prime Minister said people should not be inside the homes of their friends and families - unless it is to access gardens.
He continued: "But to control the virus everyone needs to stay alert and strictly stay 2 metres apart from those you do not live with".
"These changes meant that friends and family can start to meet their loved ones - perhaps seeing both parents at once or both grandparents at once".
He told the daily Downing Street press conference: "I can not and will not throw away all the gains we've made together and so the changes we're making are limited and cautious".
From Monday, groups of up to six people will able to meet outside for picnics and barbecues across England.
He added: "We don't want people to stay overnight, we don't want people to go to other households and stay there, I'm just afraid we're not at that stage".
We'll bring you more news as soon as we have it, but do keep in mind to keeping washing your hands and maintaining social distancing when you're out and about.
Professor Chris Whitty urged caution that maintaining two metres was "essential", adding: "This risk has not gone away".
"Quite frankly I'm not certain - right now - that an inquiry into that matter is a very good use of official time", the PM said.
Appearing alongside Johnson at Thursday's coronavirus briefing, Sir Patrick Vallance, the government's chief scientific adviser, was asked for his view on the matter.
West says he is still being charged £5,000 rent per week, and is paying for utilities as he has a live-in manager: "At the moment the site is probably costing me £7,000 a week".
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