Simon Case has been confirmed as the UK’s new top civil servant, with the prime minister saying he would do a “fantastic” job as cabinet secretary. The 41 year old replaces Mark Sedwill, who announced at the end of June that he would stand down from his twin posts of national security adviser and cabinet secretary. Case won the trust of Boris Johnson when he was drafted into Downing Street to help tackle the coronavirus pandemic, and then promoted to permanent secretary at No 10, after a stint as private secretary to the Duke of Cambridge. A career civil servant, Case has previously held several senior roles, including principal private secretary to David Cameron and Theresa May, and director of strategy at the government’s intelligence-gathering agency, GCHQ. Johnson said: “Simon will make a fantastic cabinet secretary and head of the civil service. His years of experience at the heart of government and working for the royal household make him ideally suited for this crucial role.” Case said: “Over these few months of working on the Covid response, I have seen how much hard work is being done by the civil service to support the government and our country through unprecedented times. It is a privilege to come into this role to lead a service that is working day in, day out to deliver for people right across the country.” The prime minister’s chief Brexit negotiator, David Frost, has been handed the national security role that was the other part of Sedwill’s job. Theresa May publicly condemned that decision, calling Frost, “a political appointee with no proven expertise in national security”. Sedwill’s departure was regarded as a victory for Dominic Cummings, Johnson’s most senior aide, who had a tense relationship with Sedwill, and Michael Gove, the cabinet minister who is pushing through a restructuring of government departments. Sedwill is one of a number of senior civil servants who have departed in recent months – the most recent being the Department for Education permanent secretary Jonathan Slater, who was pushed out after the exams debacle. In Tuesday’s statement, Johnson said, “I would like to thank Mark Sedwill for his outstanding service to the government and the country as a whole. After serving for decades with great distinction, I believe he has earned the gratitude of the nation.” Case’s appointment comes as Cummings continues to shift the balance of power towards the centre of government, with a newly refurbished office at 70 Whitehall staffed by officials and political advisers where decision-making is expected to be concentrated. Government communications are also being dramatically centralised, with departmental press offices expected to be cut back at the expense of a beefed-up Downing Street operation, run by Johnson’s director of communications, Lee Cain.