Leicester has become the first area of the United Kingdom to see a localised lockdown following a surge in the number of coronavirus cases in the city.
What is closing down and why?
The press conference heard that number-crunching so far, including data from around 800 people in hospital with Covid-19 infection, had shown hotspots in parts of the city.
When asked how people would be stopped from travelling outside the city, he said: "We're recommending against all but essential travel both to and from and within Leicester, and as we saw during the peak, the vast majority of people will abide by these rules".
Residents have been advised to "stay at home as much as you can", while members of the public outside of the city have been told to avoid all non-essential travel to the region.
The planned easing of some restrictions in England on Saturday will not go ahead in Leicester.
Mr Hancock said there had been "a number of positive cases in the under-18s" detected through coronavirus testing.
He said: "Given the growing outbreak in Leicester we can not recommend that the easing of the national lockdown set to take place on July 4 happens in Leicester".
Schools will stay open for vulnerable youngsters and children of critical workers as they did before and people will be able to travel for childcare.
Responding to reports that a local lockdown could be enforced, Johnson warned that the United Kingdom is not out of the woods yet, saying "We are concerned about Leicester, we are concerned about any local outbreak".
What geographical area is covered?
Mr Hancock said the measures will apply not just to the city of Leicester but also "the surrounding conurbation including, for example, Oadby, Birstall and Glenfield".
Leicester has such a serious coronavirus situation that it's been put back in lockdown all by itself.
"But we've got it now, we are collaborating with he government, we will cooperate with this", he said.
How will it be enforced?
The Health Secretary told BBC Breakfast on Tuesday that the Government was not making non-essential travel illegal, but said it would if it had to.
Britain's health minister has said the government will change the law to enforce the local lockdown in Leicester.
Mr Hancock added: "We are providing funding for local support".
"We have had a huge dialogue with the authorities about the concept of neutral venues", Masters told MPs at a Digital, Culture, Media and Sport (DCMS) committee evidence session on Tuesday.
Mr Hancock said the Government is "still getting to the bottom of" the reasons why the outbreak in Leicester has occurred.