Simon Case, Boris Johnson’s surprise choice to become the UK’s most senior mandarin, could well resist attempts to politicise the civil service, according to his allies. Those close to the new cabinet secretary said that the 41-year-old has been “imprinted” with the values of public service, and has the skills to protect senior civil servants as well as win over the prime minister’s most zealous advisers such as Dominic Cummings. Case’s difficulty may be winning over mandarins who have so far survived a Whitehall cull during which five permanent secretaries have resigned. Some remain suspicious of his youth and inexperience; he has never run a big-spending department. Case, the youngest appointee to the job since 1916, won over Johnson when he was drafted into Downing Street to help tackle the coronavirus pandemic. He was promoted to permanent secretary at No 10, after a stint as private secretary to the Duke of Cambridge. He 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. Among those who expect the new cabinet secretary to thrive is the celebrated Whitehall historian Lord Hennessy, who supervised Case’s PhD on the functioning of the joint intelligence committee during the early cold war. “I am one of those who is increasingly worried about the increasing politicisation of the senior civil service, or at least the dangers of it. This [appointment] is a beacon of hope because he is a public service man through and through. “He believes in speaking truth unto power and all the great virtues of the grand tradition. It goes through to his last fibre,” Hennessy said. Hennessy said that it was obvious while supervising Case that he was destined for high office. “He had a muscularity of intellect and masses of intellectual curiosity, plus precise organisational gifts which you don’t usually see in students. “There is nothing flash or histrionic. He is one of those people you find every now and again in professional life who are so capable that you don’t mess around with them because they are a level above,” he said. Hennessy said Case had the knowledge of history and the intellect to take on the task to rebuild the economy and public services following the devastation of the Covid-19 pandemic. “His focus will be to steer our country through the greatest challenge we have faced since the second world war, and secondly to make sure that the reconstruction that comes out of it is not just back to business as usual with political recriminations,” Hennessy said. Hennessy’s trust in Case has been challenged by some who are concerned that he has been promoted at such a rate that he lacks experience of how to run unwieldy Whitehall departments such health, education or the Treasury. Lord Kerslake, the former head of the civil service, said Case would have to win over staff bruised by the Johnson government’s recent changes. “I wish him well; he is clearly a capable person and has worked at the centre of government for some time and has the confidence of the PM. But he has less experience on operations than many. He hasn’t run a major department and he will have to think about how he connects with those who have run big operations,” he said. Others wonder whether Case could have done more to stop the sacking of Jonathan Slater last week as permanent secretary at the Department for Education following the row over A-level and GCSE results in England. Case’s rapid rise within the civil service began in 2006 at the Ministry of Defence. Over the next eight years he held roles in the Cabinet Office and the Northern Ireland Office, where he coordinated intelligence, before moving on to GCHQ. According to the Spectator, Case is also suspected of writing a piece by a senior GCHQ officer named “Peter”, in which the author defended GCHQ’s work at the height of the crisis triggered by the revelations of Edward Snowden in the Guardian and elsewhere. “We do not expect to persuade everyone to support what we do, but GCHQ certainly does bear a responsibility to make sure the discussion about us is based in reality,” Peter wrote in 2015, as he argued why mass data collection was, in the agencies view, necessary in the struggle against terrorism. Case, known for working long hours, first caught the eye of Johnson, the then foreign secretary, when working for Cameron as a principal private secretary, sources said. He was part of the team involved in the Brexit talks but left in 2018 to become Prince William’s private secretary – a job which left him negotiating with the office of Prince Harry and his wife, Meghan, as they sought to step back from life as senior royals. A running and cycling enthusiast who has a family home near Cheltenham and occasionally watches West Ham, he will arrive in the office next week. “Do not expect him to leave his desk in a hurry – he tends to stick around and make his mark,” said a former colleague.