Dominic Cummings, chief aide to Boris Johnson, in Number 10.
Sir Mark Sedwill has long been accused of holding too much influence in Whitehall, because he occupied the dual roles of national security adviser and cabinet secretary. In the vacuum of Theresa May’s Downing Street, he amassed the power to oversee defence reviews, coordinate intelligence agencies, dictate the direction of the entire civil service, and shape the structures of the cabinet office. Little wonder, then, that some advisers see him more as a political competitor than a neutral facilitator. Now, in Dominic Cummings’ Downing Street, he looks set to be locked out of his own fiefdom.