Britain's ambassador to the US said Donald Trump abandoned the Iran nuclear deal in an "act of diplomatic vandalism" because it was agreed by his predecessor Barack Obama, according to the latest leaked cables.The May 2018 memo was said to have been written by Sir Kim Darroch after a visit to the US by Boris Johnson, then foreign secretary and now frontrunner for the Tory leadership, who was making a final attempt to keep the US in the deal.Sir Kim told Mr Johnson: "The outcome illustrated the paradox of this White House: you got exceptional access, seeing everyone short of the president; but on the substance, the administration is set upon an act of diplomatic vandalism, seemingly for ideological and personality reasons - it was [previous US president] Obama's deal."Moreover, they can't articulate any 'day-after' strategy; and contacts with State Department this morning suggest no sort of plan for reaching out to partners and allies, whether in Europe or the region."The Iran deal, which is still backed by Britain, France and Germany, eased sanctions in return for cuts to Iran's nuclear programme.It is the second set of leaked emails published by the Mail on Sunday - last weekend they revealed that Sir Kim had described Mr Trump as "inept" and "dysfunctional", a revelation that eventually led to the ambassador's resignation.Met warns that leakers will 'face the consequences'The Met Police Counter Terrorism Command, which is responsible for investigating allegations of criminal breaches of the Official Secrets Act, is investigating the source of the leaks.More from Sir Kim DarrochAssistant Commissioner Neil Basu also warned that publishing further details of the ambassador's communications could be in breach of the Act, words that prompted a furious reaction from journalists and some politicians.On Saturday Mr Basu said police had "no intention" of preventing stories being published that were in the public interest.However, he added that police were aware that other cables "remain in circulation" and publishing those "now knowing they may be a breach of the OSA" could breach the act.Political journalist Isabel Oakeshott defends reporting on the leaked diplomatic cablesResponding in light of its latest splash on the leaked cables, The Mail On Sunday said: "The media must be free to publish such information, in the public interest, as long as it does not endanger lives or national security," the spokesman said."Our readers across the globe now have important information about how Britain tried, but failed, to stop President Trump abandoning the Iran nuclear deal."What could be more in the public interest than a better understanding of how this position was reached, which may have serious consequences for world peace?"In response to the latest leak, a Foreign Office spokesman said that the person responsible for the leak should "face the consequences of their actions".The spokesman added: "It's not news that the US and UK differ in how to ensure Iran is never able to acquire a nuclear weapon; but this does underline that we do not shy away from talking about our differences and working together."