In Leaks, U.K. Ambassador Casts Trump as Ineffective and Erratic

The diplomat noted that Mr. Trump has regularly survived scandals in the past, and suggested that he could win a second term as president. “Trump may emerge from the flames, battered but intact, like Schwarzenegger in the final scenes of ‘The Terminator,’ ” Mr. Darroch wrote, referring to the 1984 science-fiction film.

He warned of “real risks on the horizon,” as Mr. Trump guided United States policy away from consensus with Britain. “This ‘America First’ administration could do some profoundly damaging things to the world trade system: such as denounce the W.T.O., tear up existing trade details, launch protectionist action, even against allies,” he wrote. “It could further undermine international action on climate change, or further cut U.N. funding.”

He noted that Mr. Trump’s decision to order a missile strike on a Syrian air base had been a political success, but warned that “a less well judged military intervention is not inconceivable.”

There is some history to the relationship between Mr. Trump and the British ambassador. Shortly after he took up the post in 2016, a memorandum by Mr. Darroch was leaked, suggesting that Mr. Trump would be “open to outside influence if pitched right.”

Mr. Trump then recommended, via Twitter, that his friend Mr. Farage, then the leader of the U.K. Independence Party, be appointed as ambassador to Washington in Mr. Darroch’s place. “He would do a great job!” Mr. Trump wrote.

A Downing Street spokesman responded swiftly that Mr. Darroch had the government’s support. A diplomat for 29 years, Mr. Darroch has served as Britain’s permanent representative to the European Union, as head of the Foreign Office’s press office and as national security adviser.

Among other revelations in the leaked cables:

• British officials cast Mr. Trump’s state visit as a strategic coup, writing that his team was “dazzled” by their reception. “These are close contacts, with whom we have spent years building relationships: These are the gatekeepers and the ‘Trump whisperers,’ the people we rely upon to ensure the U.K. voice is heard in the West Wing.”