Boris Johnson has called for a "heavy dose of caution" as lockdown rules were eased despite concerns over the Indian coronavirus variant.
The Prime Minister said "now everyone must play their part" as England pushed ahead with the third stage of the road map out of lockdown on Monday.
Pubs and restaurants will be able to welcome customers back indoors, visits to the homes of friends and family can resume and the foreign holiday ban has ended.
Hugs and other physical contact between households are also permitted for the first time since restrictions began more than a year ago.
But the measures were eased as top scientists called for caution and warned of a "perilous moment", with the Indian variant feared to be as much as 50% more transmissible than the Kent strain.
In a statement, Mr Johnson said : "Together we have reached another milestone in our road map out of lockdown, but we must take this next step with a heavy dose of caution.
"We are keeping the spread of the variant first identified in India under close observation and taking swift action where infection rates are rising."
He said the "current data does not indicate unsustainable pressure on the NHS", and that second vaccine doses are being accelerated to give the greatest protection to the most vulnerable.
"But now everyone must play their part – by getting tested twice a week, coming forward for your vaccine when called and remembering hands, face, space and fresh air," he added.
Ministers are hoping surge testing and vaccines will allow a safe opening up of the nation, with jabs due to be extended to the over-35s this week.
But Health Secretary Matt Hancock did not rule out the possibility of imposing local lockdowns in areas such as Bolton to tackle the Indian variant, which he warned could "spread like wildfire".
The Liverpool Echo sends newsletters on a wide range of topics – including our daily news bulletin, now going out three times a day.
There are others on what's on, politics, court news, Knowsley, Wirral, and arts & culture, as well as both Liverpool FC and Everton FC.
Signing up is free and it only takes a minute for you to get the biggest stories, sent straight to your inbox.
How to sign up for an Echo Email Update
1) Go to our dedicated newsletter page at this link.
2) Put your email in the box where indicated
3) Tick as many boxes as you like, for each newsletter you want.
4) Press Save changes and that's it!
He said there are more than 1,300 cases of the Indian variant of concern, which is "relatively widespread in small numbers" and is becoming "the dominant strain" in Bolton and Blackburn.
But offering good news over plans to ease restrictions without unleashing a fresh wave of infections and deaths, Mr Hancock said there is "new very early data" from Oxford University giving confidence that existing vaccines work against the variant.
"That means that we can stay on course with our strategy of using the vaccine to deal with the pandemic and opening up carefully and cautiously, but we do need to be really very vigilant to the spread of the disease," he told Sky's Sophy Ridge On Sunday.
"We have a high degree of confidence that the vaccine will overcome."
Cinemas, hotels and B&Bs can also reopen, with the "rule of six" applying indoors and the order to physically distance having ended between friends and family.
The easing came after official figures showed more than 20 million people have received both vaccine doses, covering more than 38% of UK adults, while more than 69% had received at least one.
Sir John Bell, Oxford's regius professor of medicine, said the result of lab experiments investigating whether the vaccine neutralises the Indian variant "looks OK".
"It's not perfect, but it's not catastrophically bad," he told Times Radio, adding there is only "a slight reduction in the ability to neutralise the virus".
The Health Secretary said there had been no known deaths from the Indian variant in Bolton of somebody who has received both jabs.
Five people have been in hospital with it after receiving their first vaccine dose, while one person who had received both doses had been admitted "but that person was frail", Mr Hancock told The Andrew Marr Show.
With surge testing also under way in areas of Blackburn, Sefton and London, Government scientific adviser Professor Sir Mark Walport warned it will be "extremely important" to keep an eye on the numbers over the next few weeks.
He told Ridge that "it's fair to say it is a perilous moment" and said "my personal judgment is that I will do things outside as far as possible".
Chairwoman of the Commons Home Affairs Committee Yvette Cooper suggested the foreign holiday ban should not end as scheduled on Monday, as it is replaced by a traffic light system of restrictions.
The Labour MP told the BBC's Marr: "The Government needs to slow down its plans. I don't understand why it's lifting some of its international travel restrictions tomorrow. I think they should be being much more cautious about that."
But Mr Hancock said people should not travel to countries not on the green list "unless it's absolutely necessary, and certainly not for holiday purposes".
"The red and amber list countries are places that you shouldn't go to unless you have an absolutely compelling reason," he told Times Radio.
Though the Government is continuing with Monday's relaxation, Mr Johnson has warned the Indian variant could jeopardise plans to end legal restrictions on June 21.
Clubs and gatherings of more than 30 people indoors will remain prohibited until the fourth and final phase of the road map.