The British ambassador to the U.S. resigned on Wednesday, days after leaked cables that criticized President Trump escalated tensions between the two close allies.

Kim Darroch’s resignation came one day after Trump bashed him as a “very stupid guy” and “pompous fool,” and his tenure became a flashpoint in the race to replace outgoing British Prime Minister Theresa May.

“Since the leak of official documents from this Embassy there has been a great deal of speculation surrounding my position and the duration of my remaining term as ambassador. I want to put an end to that speculation. The current situation is making it impossible for me to carry out my role as I would like,” Darroch wrote in his resignation letter, released by the British Foreign Office.

Foreign Office chief Simon McDonald said he accepted Darroch’s resignation with “deep personal regret.”