(Bloomberg) -- President Donald Trump abandoned the nuclear pact with Iran last year because it was signed by his predecessor Barack Obama, according to the latest U.K. diplomatic cables published in a British newspaper.

The emails, reportedly from Kim Darroch, who was Britain’s ambassador to the U.S. until he quit last week following the first batch of leaks, center on Boris Johnson’s last-ditch visit to Washington in May 2018, when he was still foreign secretary. Johnson, now closing in on the prime minister’s position, tried in vain to get Trump to stick with the nuclear deal.

According to the Mail on Sunday, the leaked emails suggested Secretary of State Mike Pompeo showed signs he disagreed with Trump’s position. Darroch also described how Trump’s advisers were at a loss to explain why the president was so determined to scrap the deal and they had no idea what to do next. The Trump administration “is set upon an act of diplomatic vandalism,” Darroch concluded in a cable sent after the Johnson meetings and leaked to the Mail.

The initial controversy over the diplomat’s cabled comments, in which he criticizing the Trump administration as “inept” and “dysfunctional,” developed into a key element of the latest jousting between Johnson and Foreign Secretary Jeremy Hunt for the Tory crown. It escalated further Saturday and even united the contenders when the Metropolitan Police issued a statement on Friday warning journalists to hand over any state secrets.

The Met backtracked on Saturday, saying the police had “no intention of seeking to prevent editors from publishing stories in the public interest in a liberal democracy” but warning that any breach of the Official Secrets Act would constitute a criminal offense.

According to the Sunday Times, authorities have identified the person responsible for leaking the documents to the Mail. The suspect had access to historical Foreign Office files, which would rule out a computer hacker being responsible, according to the Times.

The Mail’s report last Sunday, which quoted Darroch describing Trump’s White House as “uniquely dysfunctional” and given to “knife fights,” enraged the president and ultimately cost the ambassador his job. Johnson declined to support the envoy in a TV debate on Tuesday, prompting Hunt to say it showed Johnson wouldn’t face up to the U.S. president if he becomes premier. Darroch quit the next day.

As the deadline nears for Conservative Party members to post their ballots for who’ll be the next prime minister, Johnson still looks like the front-runner to enter 10 Downing Street this month.

According to the latest Opinium poll, 53% of Tory voters would back Johnson, compared with 29% for Hunt. The numbers were even stronger for Johnson when the survey asked who would make the stronger leader. On a variety of metrics in the survey, Hunt leads only on one measure -- competence.

To contact the reporter on this story: James Ludden in New York at jludden@bloomberg.net

To contact the editors responsible for this story: Matthew G. Miller at mmiller144@bloomberg.net, Steve Geimann

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