Hogan, Gabriel Patrick Sarsfield (1901–89), civil and public servant, was born 18 March 1901, the second child of Patrick J. Hogan, chancery registrar of Waterloo Place, Dublin, and Katherine Hogan (née Murphy). Educated at the Catholic University School and UCD, he garnered many scholarships and prizes before graduating with a first-class honours BA (1921). During his final year at UCD, while studying for his LLM (1923) and reading for the bar at the King's Inns, he became president of the students’ representative council (1922–3) and a member of UCD's governing body (1922–6).
Hogan was called to the bar in Hilary term 1923, before being chosen to be one of the first two administrative officers in the newly established Irish civil service. Attached to the Department of Finance, he served as private secretary to Joseph Brennan (qv) (March 1923 to April 1925) and Ernest Blythe (qv) (April 1925 to January 1927). In the course of 1925 relations between Brennan and Blythe deteriorated to such an extent that Hogan became the main conduit of communication between the two men. Matters reached a low point on budget day 1926, when Brennan left Hogan alone to deal with a discrepancy of £100,000 in the revenue figures only hours before the minister's speech in the dáil. Hogan arbitrarily increased the figure for postal revenue by £100,000 to make it appear that the revenue and expenditure figures balanced. In January 1927 Hogan was appointed as parliamentary and estimates clerk and in 1937–8 he served as secretary to the committee on economy in public service salaries; he was then attached to the Department of the Taoiseach, where he was secretary to the cabinet committee on emergency plans (1938–9). In 1939 he was promoted to acting principal in the Department of Finance and during the second world war established and managed exchange control (1940–53).
After the war, Hogan administered Marshall aid in Ireland as chairman of the liaison committee, and between 1947 and 1953 represented Ireland on the sterling area committee and at other financial and trade negotiations worldwide. He became an assistant secretary (finance) in 1948 and in this role had to contend with the devaluation crisis of 1949 and the sterling area crisis of 1952. In 1956 he was passed over for promotion to departmental secretary (when T. K. Whitaker was appointed) and in 1961 retired from the Department of Finance. He became executive chairman of Irish Steel Holdings, of which he had been a director from 1947 and chairman from 1956; he later wrote A history of Irish steel (1980). He was also a director (from 1956) and chairman (from 1964) of Irish Life Assurance, chairman of Min Fhéir Teoranta (1954–5), and a director of United Dominions Trust (Ireland; from 1963) and Ceimici Teoranta (1939–56). He was a member of the Economic and Social Research Institute, the Institute of Public Administration, and Statistical Research Society, and in 1964 he served as chairman of a commission on public and bank holidays.
Hogan was a talented rugby player in his youth, and his appetite for the game did not decrease with age. On retiring from playing he became an international selector and president of UCD and Lansdowne clubs. He was president (1948–9) and trustee of the Irish Rugby Football Union, Irish representative on the International Rugby Board (1946–71), and honorary vice-president of the South African board. In his spare time he also lectured on public finance at TCD (1943–6) and UCD (1946–61). He died 22 November 1989 in Dublin.
In 1927 Hogan married Sheila Boland, daughter of Charles J. Boland, chief valuer in Ireland; they had two sons and two daughters and lived at Clogheen, Shelbourne Road, Dublin. Their son Paul, an art student, took one of the paintings from the Hugh Lane (qv) collection in the Tate Gallery in London in 1956 to draw attention to Ireland's claim for the Lane bequest.