Theresa May did everything she could to accommodate Donald Trump. She was the first leader to visit him as president. She offered him a state visit to the United Kingdom at a much earlier stage in his tenure than his predecessors had received one. She uttered nary a word of criticism of his administration. She had a foreign secretary, Boris Johnson, who Trump likes. She accepted without protest when Trump’s decisions went against her advice—on climate change and the Iran deal, in particular.

Trump actively undermined May on at least a dozen occasions—whether by interfering in investigations into terrorist attacks or criticizing her Brexit strategy—but every single time, the prime minister turned the other cheek. She went out of her way to make the state visit a success. The president brought his extended family to London and seemed to treasure every moment. Trump could not have wished for a prime minister who was less demanding or more sycophantic.

Trump gave May nothing in return. Her government’s extraordinary generosity and tolerance of the intolerable could not even save the U.K.’s ambassador, Kim Darroch, from the president’s wrath. After the ambassador’s cables were leaked to the Daily Mail, Trump denounced him as a “pompous fool” who had not served the U.K. well. He declared that his administration would no longer deal with him. Darroch was immediately disinvited from a White House dinner with the emir of Qatar. He resigned this morning.

This brings U.S.-U.K. relations to a new postwar low. The president’s casual cruelty toward friends and the failure of Darroch’s many friends inside the Trump administration to say anything publicly on his behalf speak volumes about how much value the Trump administration places on alliances.

Darroch’s crime was to state the obvious: that the Trump administration is inept and dysfunctional. Gérard Araud, who served as France’s ambassador to the United States for four years, told me that “anyone who has any experience of Washington would agree” with Darroch’s assessment. “There is no bureaucratic process anymore,” Araud said. He offered Syria as an example: “When Trump announced the withdrawal of U.S. forces, nobody in the administration—not Bolton, not the head of the CIA, not the chairman of the Joint Chiefs—knew he would take this decision. They did not know what it meant. Syria was just one of countless examples. Trump makes these decisions from the hip. No one knows what he will decide or what will happen the day after.”

The administration’s brazen hypocrisy on what is expected of ambassadors is unsurprising but still shocking. Gordon Sondland, the U.S. ambassador to the European Union, has been scathing in his criticism of Brussels, calling the European Commission “out of touch with reality” and “off in the clouds.” In a New Year’s Eve interview on BBC Radio 4, Woody Johnson, the U.S. ambassador to the U.K., said he had traveled throughout the United Kingdom and found the people desperate for new leadership. Richard Grenell, the U.S. ambassador to Germany, began his term by calling for the United States to shame Germany on defense spending, and said he wanted to empower Trumpian conservatives in Europe. And this is what they have said on the record. One can only imagine their private briefings to the president.

I asked Araud if the United Kingdom should retaliate by restricting the U.S. ambassador’s level of access in London. He responded with a resounding no. There would be no reciprocity. “The U.S.” he said, “is playing in a different category. Ultimately, politicians do not care about ambassadors. They will not create an existential crisis over the fate of a diplomat. If necessary, they will make the sacrifice.” Darroch “is the victim of a political game in London.” Araud acknowledged that if his own cables had been leaked while he served as ambassador, he would have been recalled to Paris after a short interval. For this reason, he took extraordinary precautions in how he communicated his private impressions of the Trump administration to Paris.

There are important lessons to be learned. For the United Kingdom’s next prime minister, it is obvious that flattery and sycophancy are not enough when dealing with Trump. In one cable, Darroch noted that Angela Merkel and Emmanuel Macron were busy distancing themselves from Trump but warned London: “I don’t think we should follow them.” He was wrong. The United Kingdom needs to fight its own corner. Trump respects only power and leverage.

The problem for London, as Araud told me, is that “the U.K. is trapped by Brexit.” Its positions on Iran, climate, and trade are almost identical to those of continental Europe, but it is leaving Europe and so has no natural allies to turn to. The United Kingdom hoped to survive because of the special relationship, but in Trump’s Washington, Araud said, “alliances don’t matter and there is no sentimentality. The past is increasingly irrelevant.” It’s not just Trump. “Americans are not romantic; all that matters is what you are doing.”