If there is any fragile encouragement to be squeezed out of Boris Johnson’s letter to the European Union this week, it is perhaps the fact that he wrote it at all. After four weeks of acting as if the EU does not exist, the existence of the letter is at least an implied recognition that the relationship with the EU matters. For nearly a month, Mr Johnson’s government has also promoted the fiction that a no-deal Brexit is an acceptable prospect for Britain. So when Mr Johnson starts his letter by saying that he very much hopes the UK will be leaving with a deal, it is just about possible to muster some carefully guarded optimism that he may actually mean it.

Yet the content of what he wrote makes a mockery of any such conclusion. In fact it is difficult to see how Mr Johnson could have done less than he does in the letter to Donald Tusk. At the core of the letter is the statement that the Irish backstop is not viable. The letter then excoriates the backstop as undemocratic, a brake on UK trade and regulatory policy and a threat to the Northern Ireland peace process. In most respects, this is the opposite of the truth. In some ways it is downright mischievous. The letter is more like one of Mr Johnson’s fact-free and irresponsible newspaper concoctions than a serious diplomatic approach to solving an impasse that imminently threatens British economic stability, trade, jobs, constitutional cohesion and security.

It is important to remember what the backstop is. It is a customs and regulatory arrangement of last resort to address the unique situation in Ireland, for which Britain has shared legal and moral responsibility. It is designed to maintain an open and seamless border in Ireland in perpetuity. It would only apply if the UK and the EU cannot agree, by the end of the transition period, to a deal maintaining such a border. That is made more difficult by the tension between the UK government’s insistence on leaving the customs union and the single market, and the UK’s obligations under the Good Friday agreement which ensures the “demilitarisation” of the border as part of the peace process. Theresa May’s hope that ways could be found, amid mutual trust, of reconciling these objectives over time led Britain to propose such a backstop, to which the EU agreed. It should have been supported. But it split the Conservative party and triggered the overthrow of Mrs May by Mr Johnson.

The argument therefore directly pits the wish of the ruling hard-Brexit wing of the Tory party to deregulate the UK economy against Britain’s historic responsibilities to maintain peace in Northern Ireland and good relations with its neighbours in the Irish Republic. Polls, including one this week, show that what Mr Johnson proposes is rejected by the people of Northern Ireland (who also voted to remain in the EU back in 2016). They would prefer a regulatory border between Northern Ireland and Britain rather than between the two parts of Ireland. The US Congress has also said it will block any UK-US trade deal that undermines the peace process. Mr Johnson’s letter, with its brusque demand that the backstop must be scrapped, is both a dangerously frivolous threat to Ireland north and south and a gamble with his already highly tendentious trade aspirations.

It is easy to conclude that the letter is not a credible attempt to negotiate an alternative to the backstop at all. It contains two shoddily unreliable suggestions. One is to create “alternative arrangements” by the end of the transition period “as far as possible”. The other is to look “constructively and flexibly” at other commitments. In neither case is there any detail. If this is an opening bid in a process that is seriously intended to result in a deal with the EU, it is an extraordinarily reckless way of going about something on which so much rests.

Unsurprisingly, Mr Tusk has rejected all this because Mr Johnson offers no alternatives. Any possibility of progress towards a deal now rests on meetings this week at the G7 summit in Biarritz. Angela Merkel seemed to imply on Tuesday that she, at least, is in the business of being serious about trying to reconcile Brexit with the Irish peace process. The question facing her and all of us is whether Mr Johnson is capable of being serious too.