Speaking in the House of Commons last Monday - following his ministerial broadcast the previous evening - Boris Johnson noted: "Different approaches by the devolved administrations are to be welcomed where those are appropriate to their specific needs. But overall, and I think that all leaders of the devolved administrations would confirm this, there is a very, very strong desire to move forward as four nations together."
Yet, the fact that three of those four nations made it pretty clear that they weren't keen to follow his lead and speed on easing lockdown restrictions suggests that the "move forward" together line will be difficult to hold; particularly if the 'R' rate levels are not consistent across the UK.
There are, of course, a number of political/constitutional factors at play in all of this. It suits both the SNP and elements of nationalism within Northern Ireland to ensure that there is a significant gap between the "English" (by which they really mean Boris Johnson, Dominic Cummings and the Conservative Government) approach to dealing with the Covid-19 crisis and the approach of the regions.
Different approaches paint a picture of a disunited kingdom; and lack of unity, be it on Brexit or Covid-19 (or anything else, for that matter), is crucial to the agenda of those who support the break-up of the United Kingdom.
As a recent piece in The Economist puts it: "Nicola Sturgeon makes it her business to find ways of highlighting differences - sometimes real, sometimes contrived - between the way that the Scottish and United Kingdom Governments do things. She normally treats the UK Government's difficulties as opportunities for point-scoring."
In other words, it's her version of what used to be known by Irish republicans as the "England's misfortune is Ireland's opportunity" card.
Crisis is often helpful for local nationalism. It allows elements in the devolved regions to make the case for doing things differently and better (albeit thanks to the financial largess of a central Exchequer), while expanding their support base for independence.
But in England, we have also seen the emergence of a new generation of nationalism which is beginning to question the benefits - particularly financial - of the Union in its present form. And that could be a particular problem for unionists in Scotland and Northern Ireland.
The lack of Labour (which doesn't field candidates) and Conservative MPs from Northern Ireland exacerbates the problem for unionists here, because it means that their voice isn't properly, specifically heard within those parties.
And while the DUP did increase its national profile when it was propping up the last Conservative government, the ending of the relationship was brutal and left many unionists believing Johnson's "border down the Irish Sea" proposal was a massive act of constitutional betrayal.
Arlene Foster (along with broader unionism) faces a battle on three fronts. She doesn't want a situation in which Northern Ireland is significantly out of lockstep with Johnson on tackling Covid-19, she will have renewed worries after last week's seeming admission from UK Government sources about expanding border control posts at ports and the potential impact on local businesses, and she has to find a way of keeping Sinn Fein on board because she knows that another collapse of the Assembly would probably mean the end of the entire political process.
And, on top of all that, she will worry that Johnson's decision (though nothing is ever set in stone with him) not to seek an extension to the withdrawal timetable for leaving the EU at the end of the year means that the UK would leave (possibly without a deal) at a time when there could also be a second Covid-19 surge in the long, cold, dark nights of late autumn/early winter.
For all sorts of reasons, I don't think the present DUP/Sinn Fein consensus (which is already shakier than it was a few days ago) would survive the stress of that double-whammy.
There is another problem: it's called Boris. Most unionists are wary of both his commitments and intentions.
I was at the DUP conference in November 2018, when Johnson promised to defend unionism from Theresa May's deal. I remember the roar of approval and the ovation. I also remember him supporting the deal shortly afterwards and the eventual abandoning of the DUP (under pressure from Johnson) by the entire ERG wing, which had promised to support it against any threat to Northern Ireland's constitutional status quo.
Back in November, Johnson told Conservative members at a reception in Northern Ireland to ignore all the media stories about "borders down the Irish Sea" and to bin any letters they received on the subject. Yet, a few days ago, the story changed and it became his November pledges that seemed destined for the bin.
Responding to the news, the UUP leader, Steve Aiken, said: "That this week we are now being briefed that border control posts have been agreed by London further underpins our sense that the severe political and economic consequences of the government's policy have still not been realised."
In an exchange a few months ago, a very senior figure within the DUP told me: "Unless significantly amended, the present deal (Johnson's deal last autumn) would imperil the Union, not only because of the Irish sea border, but, more seriously, it shifts the political axis from primarily east-west to north-south. For a whole range of key economic matters, the EU context will propel those who need representation to look to Dublin rather than London ... there have been times when Northern Ireland was in turmoil that there was a section of the British establishment who believed it better to get rid of the problem, rather than solving it. We are past that stage now, but English, and at times personal, self-interest seems to trump the bonds of friendship and loyalty."
That line about "... English, and at times personal, self-interest ..." was striking six months ago. It is even more striking now.
The Covid-19 pandemic was no more than a wargamed exercise at the time of the interview, so unionist fears were entirely focused on whether Johnson could be persuaded to protect Northern Ireland's position within the UK.
But now a potential constitutional crisis is unfolding against the background of the pandemic and there are concerns in some unionist quarters that their constitutional fears will take second place to Johnson's desire to "Get Brexit done" and get Britain back to work as soon as possible in order to regenerate a post-EU economy.
That, in turn, raises very difficult questions for the Northern Ireland/Great Britain relationship, the DUP/Sinn Fein relationship and the future of the Assembly.
Boris Johnson has talked a few times in the last month about his responsibility as Prime Minister of the "United Kingdom of England, Wales, Scotland and Northern Ireland". He insists he wants to keep it intact and "moving together as four nations". His responses to the pandemic and the still-on-course departure from the EU in December will, I suspect, determine the fate of the Union.
My personal fear is that his dependency on his political/electoral/party bases in England could push him in an extraordinarily reckless direction when it comes to supporting his supposed fellow unionists in all parts of the United Kingdom.