Yvette Cooper has said Peter Mandelson should "never have been appointed" ambassador to the United States, while sidestepping a direct question over whether Keir Starmer is a strong and effective leader. Speaking during a visit to Beijing, the British foreign secretary called the release of messages linked to Mandelson's appointment an "unedifying process", after the government published a second batch of documents running to more than 1,000 pages. Among the disclosures were messages awkward for ministers, including for Mr…