Four of Boris Johnson's closest aides have resigned in a turbulent day for the UK prime minister's government. A series of scandals have put Johnson's position in peril. On Thursday, Chief of Staff Dan Rosenfield, Principal Private Secretary Martin Reynolds and Director of Communications Jack Doyle all resigned. They were directly linked to the Downing Street gatherings. Head of policy Munira Mirza quit over a barb Johnson made at the opposition Labour leader. There have been calls for Johnson to resign.