Britain has left the European Union.  Boris Johnson and Dominic Cummings turned round a Conservative poll rating of barely 20 per cent, a hostile Supreme Court judgement over prorogation, Commons defeats, stalemate and resignations to deliver first a Commons majority of 80 and then Brexit itself – less than six months after the Conservatives were reduced to only a bare four MEPs under Theresa May.

Even if he achieves nothing else as Prime Minister, Johnson will be remembered for this nation-changing achievement, more monumental even than Margaret Thatcher’s economic reforms.  Tories should always honour him for it, and for seeing off Jeremy Corbyn.

So what’s at stake in the current trade negotiation with the EU is the form of Brexit, not the fact of it.  Will we be, at one of the scale, more like (say) Norway, circling within the orbit of the EU’s Single Market rules and social market consensus; or, at the other end, Australia (for example), having no trade deal at all, and trading on minimum WTO terms?

Perhaps, at some point in the future, some other Government will lean in a Norway-type direction.  But that is neither what Johnson’s Brexit deal pointed towards, nor what his election manifesto expressly promised.

On Johnson’s deal, the revised Withdrawal Agreement and Political Declaration was worse for Northern Ireland than Theresa May’s version, since it expressly separated it further from the settlement which will apply to Great Britain…

…But better for Great Britain than May’s deal, since that settlement gives it greater potential to shape its own economic destiny as an independent state.

On the Conservative Manifesto, that document expressly committed the Prime Minister to a future relationship “based on free trade and friendly cooperation, not on the EU’s treaties or EU law”…

…And to “not extending the implementation period beyond December 2020”.  Given those commitments, we’re surprised that anyone was surprised that the Government made it clear this week that it keep that pledge.

The thrust of the public objection to doing so came from the now reduced Remainer residue – the diehard remnants of the campaigners who sought a second referendum less than a year ago.

It was that the start of 2021 would be a bad time for more friction in trade between the UK and the EU, because of the effects of the Coronavirus.

But the heart of the economic case for Brexit was always what this site called short-term pain for medium-term gain – in other words, trading off more friction with the EU for greater spending, regulatory and tax freedoms overall.

There is no guarantee that the end of transition will be any more or less disruptive in two years than it will be in December.

In any event, the real objection of those former Remainers to not extending wasn’t the public one.  Rather, it was that ending the implementation period will make it easier for Britain to begin leaving that EU orbit.

In other words, the campaign to extend transition was essentially part of the push to keep Britain within it – and make it more like Norway and less like Canada or Switzerland – or Australia, if there’s no trade deal at all.

However, the sum of the matter is that this ship is already sailing.  The economic arguments for and against Brexit were tested in the 2016 referendum.  Leave won.

Johnson then refined them further, proposing “a new relationship based on free trade and friendly cooperation, not on the EU’s treaties or EU law” in that manifesto last year.  He won.

The question that therefore remains is whether a trade deal will or won’t be agreed before the end of the year – which, given the legal and political exigencies, will mean that the parties need to get a negotiating move on.

And as our columnist Stephen Booth keeps pointing out, the dynamics of this negotiation are rather different from those of May’s.

It wouldn’t be true to claim that the UK wants nothing from a trade deal other than a barebones settlement.  It would like greater access for financial services, for example, and less trading friction than other third parties.

But in the last resort, Johnson seems prepared to walk away from the talks rather than concede “a role” to the European Court of Justice, to quote from the manifesto again.

Furthermore, he has a majority of 80, specifically returned on the basis of his Brexit vision and pledges, whereas May had none at all.

Additionally, the second most intractable problem in the two-stage negotiation has been resolved: the matter of where regulatory and trade barriers will run between Great Britain, Ireland and Northern Ireland.

Which leaves the hardest one of all – the role of the Court.  If the EU is willing to recognise that Johnson won’t budge, which seems to be the case, the elements are in place for a solution.

The EU wants fishing and migrant access, plus no tariffs, given its manufacturing surplus; the UK wants services and trade access, with minimum friction on rules of origin and other regulatory checks. The Prime Minister will have to be very careful on fishing, particularly given the Scottish dimension – and will want a U.S trade deal as a sign that the UK is truly entering a new era.

Michel Barnier seems to recognise that the EU will have to give up some ground on fishing, but although a trade deal looks possible on paper it also looks daunting in practice.  This negotiation is more in the hands of the member states and less in that of the Commission than its predecessor, and so vulnerable to spanners in the works.

Whatever happens, Britain has moved on from May’s Government and Brexit stalemate.  The CBI now says that it “supports the Government’s timetable”.  Keir Starmer is a dog that hasn’t barked on implementation extension.  EU alignment is becoming a niche cause.

David Cameron once suggested that the Eurosceptic Conservative Party was irritating the electorate by “banging on about Europe”.  That fate is currently reserved for the pro-EU Liberal Democrats, currently languishing on some seven per cent in the polls.