Mark Sedwill is a serious man. He has a master’s in economics from Oxford. He worked in Cairo, Nicosia, Baghdad and Islamabad over several decades as a diplomat. He was a UN weapons inspector, Her Majesty’s Ambassador to Afghanistan and served as the Nato senior civilian representative there. He became cabinet secretary in 2018 after the death of Jeremy Heywood, and left just two years later after the first wave of Covid.