Ms Truss was forced to fire Mr Kwarteng just three weeks later and bring in Jeremy Hunt, who immediately reversed almost all measures.
Mr Case’s involvement in dealing the death blow to ‘Trussonomics’ will further fuel the battle between the Tories and the civil service.
Tensions have risen over threats from the Public and Commercial Services Union to lead the Interior Ministry and Border Guard strikes.
It says that demoralized workers fear they will be forced to violate international law by implementing migration policies such as the Rwanda Plan.
Jacob Rees-Mogg, a former company secretary, said that “an official who refuses to implement a lawful policy should either resign or be fired”.
Priti Patel, an ex-home secretary, added that Whitehall officials should “respect the policies and legislation of a democratically elected government”.