DESPITE THE blood-letting of Brexit, most people in Brussels are sorry to see the UK leave the EU. They admire the contribution the UK has made and recognise British expertise in diplomacy and negotiation.

But at a stroke this week the Prime Minister, Boris Johnson, was on course with his Internal Markets Bill to shatter that reputation by breaking an agreement that he had signed.

These are uncharted waters. It is easy to see Johnson's maverick advisers urging on a weak prime minister. But with this one manoeuvre, he has undermined the UK's reputation for honesty in negotiations, undermined devolution in the UK and sown unnecessary divisions in Northern Ireland. It was no surprise the government's most senior legal civil servant resigned. It is hard to believe that even the ever-bullish Boris cannot see the risks. As he desperately seeks global trade deals he has shown the UK is not to be trusted over a binding agreement.

Back in the 1600s the phrase 'perfidious Albion' was coined to criticise England for breaking treaties. Johnson is risking that charge again, by treating an agreement he signed in January like a childhood promise made with fingers crossed behind your back to allow you to break it.

A key question is whether this is just more political posturing directed by Dominic Cummings, the Downing Street adviser who seems to control Johnson. Both cannot be so in awe of Donald Trump that they are adopting his approach to international agreements, which is to ignore them or smash them if they do not suit his interests. As the Brexit talks moved into the critical end game this week, the rhetoric on both sides was wound up. Brussels accused the UK of refusing to negotiate; the UK responded with a torpedo aimed at the waterline of the negotiating process.

It is hard to be believe that with the worst recession in history unfolding for both the EU and UK, either will allow the goal of a sensible, commercial trade agreement to be lost. Fishing rights are a big issue, but like lamb producers in the UK, the fishing industry relies on Europe for its market. It is equally bizarre that a Conservative government is willing to face isolation from its biggest trading partner because it wants to outdo the French in giving state aid to businesses. A lot of observers see this as a typically Brussels approach to negotiations. Both sides are talking tough to prepare the ground for a pull back from the brink in October.

That is no different to a deal being made over livestock or land, but legislation that could undermine trust in any agreement signed off by the UK looks a fundamental mistake. It is unlikely Boris Johnson meets any farmers, but if he did he would know that when a deal is poisoned by bad trust it is hard to recover. He signed a deal over Northern Ireland that was ill-conceived and impossible to implement. He made light of this, insisting a trade deal was oven-ready. But now the impossibility of implementation is upon him in a mess of his own making. He has offered no solution other than belligerence and that is not going to win the day in Brussels. Johnson views Winston Churchill as his hero, and would be wise to accept his advice that jaw, jaw is always better than war, war – and that applies as much to trade wars as to bullets and bombs conflicts.

On a less political issue, post-Brexit farming will be about whether the UK puts clear blue water between itself and the EU, or things develop the other way around. The EU has launched a pre-emptive strike with a plan, agreed by all 27 agriculture ministers and proposed by Germany, for the development of a compulsory EU animal welfare label.

The thinking is that in an era when resilience and sustainability are the the new buzz words, this will allow consumers to seek out meat produced in a way that reflects what they say they want. This is a lot better than the toothless Agriculture and Trade Commission the UK got instead of proper legislation to protect standards.

The interesting question in the future will be whether the UK will have to match that standard to sell in the EU, given that high standards are as much about protecting markets as pleasing consumers.