Mark Sedwill will leave his posts as Cabinet secretary, head of the U.K. civil service and national security adviser in September | Peter Macdiarmid/Getty Images
UK government’s top official standing down
UK chief Brexit negotiator David Frost to take over as national security adviser.
Updated 6/28/20, 7:55 PM CET
LONDON — Mark Sedwill, the most senior official in Boris Johnson’s government, will stand down in September, Downing Street confirmed.
Sedwill will leave his posts as Cabinet secretary, head of the U.K. civil service and national security adviser.
His departure comes after months of speculation about his position, amid reports that he has clashed with Johnson’s Downing Street team. It was announced 24 hours after Cabinet Office Minister Michael Gove gave a speech setting out the government’s plans for major reforms of the civil service, while criticizing many aspects of the way Whitehall operates.
The U.K.’s chief Brexit negotiator and close Johnson ally, David Frost, will take over as national security adviser and the government will shortly launch the search for Sedwill’s successor as cabinet secretary and head of the civil service.
Sedwill was appointed as Cabinet secretary — Whitehall’s top job — by Theresa May in October 2018, succeeding Jeremy Heywood, who had been diagnosed with lung cancer, and died in November 2018. Sedwill has held the national security adviser position since April 2017 and before that was the top official at the Home Office under May.
Sedwill will take on a new role leading a “G7 panel on global economic security,”