At the same panel discussion, Martin McTague, policy and advocacy chairman of the Federation of Small Businesses, expressed concern about a "two-speed UK" with different things happening in Northern Ireland and that an increase in trade North-South will "put pressure on the union inevitably" and weaken the links with Britain.

The remarks raised eyebrows in Northern Ireland.

"To hear David Frost rail against the EU is nothing new. But to hear him state clearly and coldly that he wants to damage North-South trade and stop Northern Ireland's growing exports to the EU single market is sickening and chilling," said SDLP Brexit spokesman Matthew O'Toole.

O'Toole and others in Northern Ireland expressed concern that Frost was not trying to smooth the flow of goods into Northern Ireland from Britain but was attempting to undermine the unique economic advantage given to Northern Ireland under the Brexit agreement to trade with the EU.

Tory fears that an all-island economy might be growing out of the complexities of Brexit are supported by trade figures showing a boom in North-South trade since the UK's exit came into effect. The value of goods imported from Northern Ireland to the Republic rose by 77 per cent in the first six months of the year, while exports from the Republic into the North rose 43 per cent.

"Trade is like water - it will find the path of least resistance. For us, this is the natural consequence not just of Brexit but the Brexit that they chose," said Stephen Kelly, chief executive of business representative group Manufacturing NI.

While North-South trade has increased, imports into the Republic from Britain fell 16 per cent. Companies, North and South, have complained about torturous volumes of paperwork that must accompany goods travelling west across the Irish Sea that make some trade, particularly for small companies, just not worth the business. British companies are among those to have lost out.

Frost's reference to the land bridge show he is concerned also about the loss of this business to Britain from the Republic and that the UK might be struggling to understand the consequences of Brexit and becoming a "third country" with all of the cross-Border checks this brings. And this is all happening before the UK switches on its own import controls on goods from the EU.

As Bobby McDonough, former Irish ambassador to the UK, Brussels and Rome, notes: Brexit is not going well

A recent YouGov poll found that 53 per cent of the British public think Brexit is going badly. A mere 18 per cent believe it is going well. The British people are remarkably astute given that the majority of MPs, as well as great swathes of the British media, are in denial.

Brexit, like TS Eliot's Macavity, continues to be something of a Mystery Cat. The Johnson government's policy agenda for implementing and celebrating the restoration of the UK's so-called "freedom" falls into two broad categories.

First, doing things the UK was perfectly free to do as an EU member state while proclaiming them to be a Brexit dividend. Second, pretending that the real negative effects of Brexit have nothing to do with Brexit. As TS Eliot might have put it, Brexit is "the bafflement of Scotland Yard, the Flying Squad's despair/For when they reach the scene of crime - Macavity's not there".

On the one hand, there are the many Brexit "triumphs" claimed by the Johnson government, developments that would have been entirely compatible with the UK's continued membership of the EU. Much of the British media has either fuelled this fiction or allowed it to go unchallenged.

While imaginary Brexit benefits became holy writ for the British tabloids, the obvious negative effects were swept under the carpet

Most obviously, there are the international trade deals through which the UK has scrambled to maintain the beneficial trade arrangements it already had through the EU.

Although the UK is now, at best, no better placed in trade terms than it was before and certainly less influential into the future, the constant trumpeting of illusory negotiating triumphs propelled trade secretary Liz Truss to become the Tory faithful's most popular member of government.

Similarly, EU membership would not have prevented the UK from participating in AUKUS, its new trilateral security pact with the US and Australia, even if poking France in the eye would have been even more foolish if the UK were still trying to work closely in Europe with its most important and natural partners.

Apparently Lord Frost is getting "itchy fingers" at the prospect of Triggering Article 16:

When David Frost addressed a half-empty room at the Conservative Party conference in Manchester on Monday, there were almost as many European diplomats in the audience as party members. But his speech was a hymn to Britain's bright future alone now that it had slipped the bonds of the European Union.

"The long, bad dream of our EU membership is over. The British Renaissance has begun," he said.

According to Frost's account of Brexit, the only blot on the sunlit landscape of fuel shortages, empty supermarket shelves and a looming cost of living crisis is the Northern Ireland protocol. And he made clear once again on Monday that Britain's patience with the EU is running out and that each day brings him a step closer to triggering Article 16.

In the coming days, Frost will send the EU legal texts based on his July command paper calling for sweeping changes to the protocol. The EU has not yet formally responded to the proposals but has ruled out renegotiating the agreement, and its offer of easements within the existing protocol is unlikely to be enough for Britain.

Having threatened Article 16 so often, the time may be approaching when Frost will have to trigger it. But as the leaders of Northern Ireland's three unionist parties said at a fringe meeting in Manchester Art Gallery, that will not achieve much on its own.

For a start, triggering the article begins a fresh round of negotiations with the EU before any action can be taken. It only allows Britain to suspend parts of the protocol and it must justify why each suspension is necessary.

So Article 16 allows Frost only to suspend the protocol in a limited and specific way and the act of triggering it will almost certainly provoke legal action from the EU. If he decides to go further by tearing up the agreement to unilaterally impose the changes set out in the command paper, the EU's response will be more dramatic, possibly including retaliation under the trade and co-operation agreement.

Even such reckless action, which could add to the supply chain problems that threaten Britain with a winter of food and fuel shortages, would not be enough to satisfy unionist leaders. As Jeffrey Donaldson stressed on Monday, they are demanding the full repudiation of the protocol through primary legislation at Westminster, and triggering Article 16 will do little to reassure them.

It is worth noting that Northern Ireland has not experienced the fuel shortages plaguing Britain, and while there have been some empty shelves at British supermarket chains like Marks and Spencer, there are alternative sources of supply and no shortages in the rest of Ireland. The EU have offered "easements" on the certification of medicines for Northern Ireland originating and certified in the UK, but none of this has been of any interest to Lord Frost and co. Their real concern is the losses being suffered by British businesses and the degree to which Northern Ireland is re-orientating its trade to Ireland and the EU.

The other thing that Lord Frost should consider is that there is nothing short of a full scale trade war between Britain and the EU that would appease unionist and loyalist leaders. They are concerned to maximise the links between Northern Ireland and Britain even if this sinks the UK as a whole.  In the same way as British Brexiteers are hardly concerned about the future of Northern Ireland, unionist do not care what damage their petty squabbles do to the UK as a whole.

It is this divergence of interests between British Tories and their erstwhile unionist allies that should worry Boris Johnson most. It is also doubtful that the White House was overly impressed by a British cabinet Minister's suggestion that Biden is approaching senility and doesn't understand the complexity of the difficulties created by the Protocol, a suggestion the Irish government was quick to rebut:

Mr Biden has warned British prime minister Boris Johnson that that the Belfast Agreement must not be put at risk by the difficulties in reaching agreement on post-Brexit trade rules between the UK and EU.

He said he feels "very strongly" about the issue and added: "We spent an enormous amount of time and effort in the United States.... and I would not like to see - nor would many of my Republican colleagues - a change in the Irish accord."

British environment secretary George Eustice later claimed that Mr Biden does not "fully appreciate" the details of the dispute over the Northern Ireland protocol.

He told Sky News it is "very complicated" and "I'm not sure he does fully appreciate all of that".

Mr Eustice also suggested that Mr Biden is "just reading the headlines, reading what the EU is saying, reading what Ireland might be saying, which is that they would like the Northern Ireland Protocol to work in the way the EU envisage."

Does the UK really want to risk a trade war with the EU and the ire of the Biden administration? They are going the right way about it, and it is Lord Frost who is running out of time rather than the EU. The EU is currently winning every battle and can afford to play a long game, while the Brexit crisis is growing every day in the UK.