Diplomat. William was born 15 December 1892, the only son of Capt. Patrick Macaulay and Elizabeth Macaulay (née Murphy) of Waterside, Co. Antrim. He was educated privately and served with a commission in the British naval volunteer rescue reserve (1915–20). He resigned his commission and joined the Irish civil service, entering the Irish Free State revenue commissioners. Joining the Department of External Affairs, in 1925 he became secretary of the Irish legation in Washington, being promoted to counsellor in 1929. He was appointed consul general in New York in 1930. In 1934 he returned to Europe as Irish minister to the Vatican. Macaulay ensured that the policies and actions of Éamon de Valera and his government were understood in the Irish College and in the Holy See. He was unusually forceful in his direct approaches to the cardinal secretary of state, explaining the limits to which the Irish bishops could involve themselves in Irish politics. At the time of his appointment to the Holy See, Ireland had no legation to Italy, and Macaulay also kept a close watch on Italian domestic politics and foreign policy. In particular, he reported to Dublin on the Italian invasion of Abyssinia in 1935 and the reaction in Rome to the imposition by the League of Nations of sanctions on Italy. Macaulay's background had led to suggestions in Dublin that he was too pro-British in outlook; he had a good relationship with the British embassy to the Quirinale and the ambassador, Sir Eric Drummond. While Macaulay was adept at cultivating such connections in the furtherance of Irish foreign policy, he was tipped off by assistant secretary Seán Murphy to limit his contacts with British diplomats, as they might be misinterpreted in certain circles in Dublin and in the Department of External Affairs.In 1937, in New York, Macaulay married an Irish-American papal duchess, Genevieve Brady, widow of Nicholas Brady, a wealthy New York Irish-American. Macaulay and his wife were close friends of Cardinal Pacelli, later Pope Pius XII. Through their mutual connections, the couple swiftly brought Irish diplomacy close to the centres of power within the Vatican, providing much high-grade information to Dublin. However, his wife died suddenly in 1938. Citing poor health, the need for treatment in the US, and the impact of the death of his wife, Macaulay sailed for North America on 1 June 1940, and resigned from his post to the Holy See and from the Irish diplomatic service on health grounds in 1941. As Irish minister to the Holy See Macaulay had exceptionally strong professional contacts with senior Vatican personnel and with members of the US hierarchy. He ensured that de Valera and Fianna Fáil remained in good standing in the Holy See and with Pope Pius XI, and he completely overcame the suspicion with which Fianna Fáil had been regarded by the Holy See in 1932. His resignation was a serious setback for Irish–Vatican relations during the second world war, as many important contacts and connections were lost, to be at best partially rebuilt by his successor, Thomas J. Kiernan. From 1940 Macaulay lived in the USA, in New York and later Connecticut. In 1958 he established the W. J. B. Macaulay Foundation in honour of Seán T. O'Kelly, which was administered through the Arts Council and provided scholarships in the creative arts. In 1962 Macaulay returned to Europe and moved to Florence, Italy, where he died 7 January 1964.