Lord Darroch of Kew and his wife during a reception to celebrate the royal wedding two years ago, before he was forced out of his job

Britain’s former ambassador to the US has described President Trump as a “terrifying” and “lethal” campaigner, in his first interview since he was forced out of the job.

Lord Darroch of Kew, 65, resigned last July when he came under sustained attack in a series of tweets from Mr Trump after condemning the administration as “inept” in leaked diplomatic cables. He failed to secure explicit support from Boris Johnson, who at the time was frontrunner to be the new prime minister.

The furore surrounding the leak of sensitive cables written by the ambassador marked a low point in transatlantic relations, with Mr Trump criticising him as “wacky”, “stupid”, “pompous” and “not liked or well thought of within the US”. He added that “we will