Holmes joined the
Board of Education in 1909, where he was to stay until 1945, except for the
First World War, when he joined the
Army and rose to the rank of
lieutenant-colonel. Holmes rose to become Director of Establishments in 1923–26, reaching the position of Deputy Secretary in 1931. In 1937, he replaced
Sir Henry Pelham as the
Permanent Secretary. During the
Second World War, Holmes was given the task of developing the so-called Green Book which served as a precursor for the landmark
Education Act 1944. He retired in 1945, to be replaced by
Sir John Redcliffe-Maud. After his retirement, Holmes served as the Chairman of the East African Salaries Commission in 1947, the Colonial Office inquiry into Civil Services of Kenya, Tanzania and Uganda, the 1948 Caribbean Public Services Unification Commission, and the Lord Chancellor's Committee on Office of Public Trustee in 1954. == Honours ==