Sir Mark Sedwill will step down from his dual role as Cabinet Secretary and National Security Adviser.
Prime Minister Boris Johnson was quick to announce David Frost, his Europe adviser, as his new National Security Adviser (NSA), taking over from Sir Mark in September when he formally stands down.
Both Sir Mark and Mr Frost are to be awarded life peerages, Downing Street confirmed, elevating them to the House of Lords.
In his letter to Mr Johnson, Sir Mark said:
“Two years ago, when my predecessor fell ill, your predecessor asked me to step in as Cabinet Secretary, and you asked me to continue to support you through Brexit and the election period.
“It was obviously right to stay on for the acute phase of the Covid-19 crisis.
“As you are setting out this week, the Government’s focus is now shifting to domestic and global recovery and renewal.”
Sir Mark added it had been “a privilege to serve” as he announced he will stand down from his roles.
The PM praised the outgoing civil servant, with more than 30 years service, for his “outstanding” work.
“It has been by any standards a massive contribution – but as PM I have particularly appreciated your calm and shrewd advice,” he wrote to Sir Mark in his responding letter.
Boris Johnson also asked Sir Mark to lead a new G7 panel on Global Economic Security as the UK assumes the presidency with a mission to ensure that “the global free trading system on which our economy is based remains fair, competitive and secure”.
Cover image: Cabinet Secretary Sir Mark Sedwill giving evidence to the Commons Public Administration and Constitutional Affairs in 2020 (Picture: PA).