Born in 1932 to the legendary colonial-era chief Musa Nyandusi, Nyachae belonged to the first crop of British-trained African administrators who also made it big in business.
He attended Torquay College, UK, between 1957 and 1959 and later Churchill College, Cambridge.
He rose through the ranks from a District officer in Kangundo and other parts of Machakos District in 1963 to a Provincial Commissioner between 1965 and 1979 and later the Head of Civil Service and Secretary to the Cabinet in the Moi administration.