Boris Johnson has said there will be no control points on the Irish border - even if the devolved governments take different strategies to easing the lockdown.
During yesterday's Downing Street press conference, the Prime Minister took public questions, including one from 'John' in Londonderry.
The PM said: "There'll be no checks, nothing is intended between Ireland and Northern Ireland and similarly you wouldn't expect anything between GB and Northern Ireland.
"What we really want people to do in this country is to look at our social distancing measures that we're proposing.
"All four nations totally understand what those social distancing measures are and apply them with common sense."
He added: "I think it's the common sense of the British people that has been so crucial and the whole of the UK in getting the R down. Everybody understood roughly what to do in the first phase and it's by applying common sense that I think we will be successful in this second phase as well."
He was asked to explain how it was "logical" for people to be able to mix in workplaces but not with family members, and how parents could possibly follow his "back-to-work" mantra if schools were still not open. Mr Johnson was also asked why people in Scotland, Wales and Northern Ireland should follow the rules when the leaders of the devolved administrations were refusing to adopt his strategy.
All three have pointedly refused to follow the lead of Westminster in dropping the "stay home" message in favour of "stay alert".
Defending the changes in Parliament, Mr Johnson said there would be "myriad hypothetical situations" in which people would come up against the "complexity" of the new rules, but added: "I know that the British public will continue to help the police, and everybody, to enforce the rules... by continuing to apply good, solid British common sense."
Earlier, in the Commons, an SDLP MP said Northern Ireland businesses fear that pro-Brexit Cabinet ministers will use coronavirus to mask the damage that Brexit will have on the economy.
Speaking during a coronavirus debate, Claire Hanna said: "I know members and certainly the government would like to give the impression that the issue of Brexit is done and dusted, but unfortunately we're still living with the Sword of Damocles hanging over us in the form of either a border in the Irish Sea or the spectre of a border on the island of Ireland if the Ireland protocol isn't honoured.
"And I'm afraid we see very few signs of good faith in working towards implementation of that which was scheduled to be in place by next month.
"And I want to remind members what an enormous breach of good faith it would be if we end up with a border because of a no-deal scenario due to the pressures of the pandemic on an already very ambitious negotiating timeframe.
"And I know of no business who wants to choose between their EU market and their market in Britain, but I do know of many who fear that ideological Brexiteers in the Cabinet will use the cover of the disruption to the economy of Covid to mask the damage of Brexit on the economy. I'm afraid that would be a fateful blow in Northern Ireland."