He was the fourth child of the surveyor John Frederick Mann and his wife Camilla Victoria, daughter of Sir Thomas Mitchell.

[3] By the mid-1890s he was secretary of the Art Society of New South Wales and on 3 April 1902 he married Mabel Beatrice, daughter of photographer J. Hubert Newman.

[5] He was chairman of the Commonwealth Art Advisory Board from 1918–1948, established to advise the Historic Memorials Committee; which from 1914, at Mann's behest, began to acquire the nucleus of a national collection.

Mann died on 12 November 1948 in Royal North Shore Hospital and was cremated with Anglican rites.

[7] On the 5 June 1930, he was formally invested with the insignia of Commander of the Civil Division of the Most Excellent Order of the British Empire.