UK PM Keir Starmer has admitted he made a mistake when he appointed Peter Mandelson as Ambassador to Washington. Starmer said he would not have appointed him if he had known Mandelson had failed security checks.Al Jazeera’s Jonah Hull reports from London. pic.twitter.com/v7jEkQlPMO— Al Jazeera English (@AJEnglish) April 20, 2026