In February 2013, Sedwill became the Permanent Secretary at the Home Office, filling the vacancy left by Helen Ghosh. Sedwill replaced Mark Lyall Grant as National Security Adviser in the Cabinet Office in April 2017. During his time as Permanent Secretary, one of the organisations the Home Office is responsible for, MI5, failed to adequately safeguard data. In 2019 Lord Justice Sir Adrian Fulford stated MI5 had a "historical lack of compliance" with sections of the Investigatory Powers Act in 2016.
Cabinet Secretary
Sedwill became acting Cabinet Secretary in June 2018, while Jeremy Heywood took a leave of absence on medical grounds, and was appointed to replace Heywood on his retirement on 24 October 2018. He is the second Cabinet Secretary never to have worked at HM Treasury, and the first whose career has been dominated by diplomatic and security work. He was described as the Prime Minister's "first and only choice" to replace Heywood, with no recruitment process taking place and some suggesting the urgency of arrangements for the UK's departure from the European Union as a reason for the quick appointment. Prime Minister Theresa May was criticised for allowing Sedwill to remain as National Security Adviser alongside his role as Cabinet Secretary, with speculation that the role was being kept for Europe adviser Oliver Robbins. In a February 2019 interview Sedwill said he would retain his role as National Security Adviser to the Prime Minister since becoming Cabinet Secretary is part of moves to make a success of Brexit. In an interview with Civil Service Quarterly, Sedwill said retaining the post would also ensure a "genuine sense of teamwork across and beyond government". In April 2019 it was reported that Sedwill had written to ministers on the National Security Council and their special advisers after The Daily Telegraph reported details of a meeting about Chinese telecoms company Huawei. Following the meeting of the council, the Telegraph reported that it had agreed to allow Huawei limited access to help build Britain's new 5G network, amid warnings about possible risks to national security. Several cabinet ministers have denied they were involved. In July 2019, The Times reported that two unnamed senior civil servants had said the 70-year-old Jeremy Corbyn might have to stand down due to health issues. The article drew an angry response from Labour, which denounced the comments as a "scurrilous" attempt to undermine the party's efforts to gain power. Downing Street said that Sedwill would write to Corbyn after the party demanded an inquiry into alleged comments. It is unclear whether he will order an investigation. Corbyn has said the civil service has a duty to be non-political. In November 2019, Sedwill blocked the publication of a document written by civil servants to cost the Labour Party's fiscal plans before a general election. Shadow ChancellorJohn McDonnell had complained to Treasury Permanent Secretary Tom Scholar in a meeting arguing it would interfere in the upcoming general election. In June 2020, it was announced that Sedwill would be stepping down from his civil service appointments in September 2020. The Telegraph said that Downing Street regarded Sedwill as "too much of a Europhile and establishment figure" to be in post through planned Whitehall reforms.
