Mr. Araud recalled a moment in 2017 when France’s foreign minister was planning a trip to Washington. The ambassador gave the State Department two months’ notice to try to get on Mr. Tillerson’s schedule. They never heard back until a day before the event, Mr. Araud recalled, only to be told the meeting would last only 20 minutes.
“So the minister didn’t come,’’ he said.
Mr. Darroch was somewhat more successful. From his time as national security adviser, he had deep contacts in the intelligence agencies in the United States, and among the permanent class of national security specialists. But even in those conversations, officials often expressed mystification about how decisions in the Trump administration were made and policy generated.
Traditionally, the British ambassador would be brought in for consultations with senior American officials about major decisions under consideration in the Middle East, or in dealing with Russia, where Britain’s G.C.H.Q. — the Government Communications Headquarters, the British equivalent to the National Security Agency — often takes the lead in gathering intelligence.
But not in the Trump era.
All are examples of the chaos that Mr. Darroch had described to his successor as national security adviser, Mark Sedwill, in a 2017 memorandum that leaked on Saturday, leading to Mr. Trump’s declaration that the ambassador to America’s oldest ally was, in effect, persona non grata.
Mr. Johnson, the front-runner in the prime minister’s race, said on Wednesday that he regretted Mr. Darroch’s departure, and that whoever leaked the ambassador’s messages should be “run down, caught and eviscerated.”
There will be a new British ambassador, presumably appointed after Parliament selects a new prime minister to replace the departing Theresa May, and seats a new government. But under current conditions it is unclear whether that diplomat’s access will be much better.
A comment from the State Department about Mr. Darroch’s departure on Wednesday blandly repeated its commitment to the “special relationship” between the United States and Britain.
The two nations “share a bond that is bigger than any individual,” the statement said, “and we look forward to continuing that partnership.”