He is more suited to wearing his T-shirts inside out with combat trousers but as Dominic Cummings launched a new "mission control" at 70 Whitehall on Tuesday he dressed for the occasion.
The Prime Minister’s chief adviser donned a dark suit with a pink shirt (but no tie) as No 10’s top team was relocated to the Cabinet Office as part of a major overhaul.
The former Vote Leave supremo and around 20 political officials, including Munira Mirza, director of the Number 10 Policy Unit, have moved to the new open-plan office in a shake up of the machinery of Government.
The 41-year-old was seconded from Kensington Palace in May.
The Prime Minister personally telephoned Prince William to apologise for poaching his right-hand man. The prince, 38, “took it well” and agreed to release Mr Case “for the good of the country”.
Mr 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.”
Mr Case said he was “honoured” to be appointed and paid tribute to Sir Mark, who initially recommended him for the permanent secretary role.
A No 10 source said Mr Case, who officially starts his new role on September 9, had already been tasked with the Government’s top priorities: "Covid, leaving the EU, saving the union and the next budget."
“Those are top of his in-tray, as set by the PM,” said the insider.
The door that currently connects 70 Whitehall to 10 Downing Street has been removed to unite the two office complexes after Mr Johnson decreed that No 10, the Treasury and the Cabinet Office must work more closely together.
Yet, on Tuesday evening there were murmurs of dissent in the Cabinet Office ranks following what some civil servants perceive as the "political" appointment of Mr Case.
According to one source: “He’s very much viewed as being in Cummings’ pocket and the PM’s yes-man.”
An ally of Mr Case said he was "very much his own man".
On Tuesday, Mr Case's predecessor Lord Gus O'Donnell said his biggest challenge would be to “restore trust in Government and restore the Civil Service's trust”.