UK 11 July 2019 Boris Johnson has failed his first big test as a potential prime minister Kim Darroch's resignation is the result of Johnson's spectacular failure to lead and to represent Britain's interests abroad. Getty Images Boris Johnson takes part in the ITV televised debate on 9 July 2019. Sign UpGet the New Statesman\'s Morning Call email. Sign-up Boris Johnson has just flunked his first big test as a putative prime minister. Following the leak of Kim Darroch’s confidential cables appraising the Trump administration, he failed to support the British ambassador to Washington in the Conservative leadership TV debate. As a result, Darroch resigned. This is an absolute disgrace. I know Darroch. Our paths have crossed at various times during my journalistic career. I have found him to be a brilliant diplomat, and as decent, honest and straight as they come. Trump's description of him as "whacky", "stupid" and "a pompous fool" could not be further from the truth. But Johnson failed to stand up to Trump. He has allowed the White House to determine who represents Britain in Washington. He chose to capitulate to pressure from the bullying US president instead of defending a civil servant whose only "crime" was to do what he was paid to do – to give his masters back in London his best and most candid assessment of the Trump administration. How does this constitute 'taking back control', or the reassertion of British sovereignty? If Johnson can't stand up to Trump on this issue, how will he stand up for British interests when it comes to negotiating a post-Brexit trade deal with the US, with Britain coming to the negotiating table as a supplicant? How will he resist Trump’s demands that we accept America’s chlorine-washed chickens, or that corporate America be let loose on the NHS? And why are he and all the other Brexiteers so determined to cosy up to the lying, racist, sexist, boastful, dictator-hugging US president – a man whom Johnson himself once described as "stupefyingly ignorant" and unfit to hold office – while burning bridges with our true friends and allies in the European Union? Johnson – a former foreign secretary who should have known better – spectacularly failed to do the right thing, to show leadership, or to defend Britain’s interests. He could very easily have defended Darroch, as Jeremy Hunt did. If Britain’s relationship with the US is indeed strong and special, it would undoubtedly have survived. Instead he sent a signal of weakness that Trump, the most transactional of presidents, will surely seize upon – and one that will have been noted by the EU’s Brexit negotiators as well. One more thing. Johnson also conspicuously failed to condemn the real villain of this lamentable saga – the person who betrayed Darroch, damaged British interests and committed a criminal offence, under the Official Secrets Act, by leaking his cables. There is little doubt in my mind that this person was a Brexiteer. The leak was made to Isabel Oakeshott, one of Nigel Farage and Arron Banks’ favourite journalists. It was placed in the Mail on Sunday, a vigorous champion of Brexit. And the net result has been to create a vacancy in Washington that prime minister Johnson can fill with a pro-Brexit zealot. Unless, that is, Theresa May takes revenge against a colleague whose treachery and disloyalty has plagued her premiership, by appointing her own man, or woman, in one of her final acts before stepping down. › Five things you need to know today: the UK-Iran clash and Labour's war with the BBC Martin Fletcher is a former foreign editor of the Times and a New Statesman magazine contributing writer and online columnist. Subscribe For daily analysis & more political coverage from Westminster and beyond subscribe for just £1 per month!