Sir Mark Philip Sedwill
is a British diplomat, public policy analyst and senior civil servant who has served as Cabinet Secretary and Head of the Civil Service since 2018 until 2020. He has also served as National Security Adviser since 2017. He was previously the United Kingdom's Ambassador to Afghanistan from 2009 to 2010 and the NATO Senior Civilian Representative in Afghanistan in 2010. He was the Permanent Secretary at the Home Office from February 2013 to April 2017. The UK government announced on 28 June 2020 that he is ‘stepping down’ from the posts at the end of September.