From 1925- 1930 Mant was a journalist with the Daily Telegraph. In 1940 he joined the AIF and saw active service in Malaya. He served for fourteen months then became Australian news editor with Reuters, returning to Malaya as a war correspondent. Grim Glory (1942), an account of the campaign in Malaya, was followed by You'll Be Sorry (1944), a personal narration of his experiences as a soldier and war correspondent, both of which were republished as The Singapore Surrender in 1992. Some of his other works include A Cuckoo in the Bodyline Nest (1992), Mant's account of being on tour with the 1932-1933 cricket tour of Australia, and books on the history of the Agricultural Societies Council of New South Wales. He also edited Soldier Boy: The Letters of Gunner W.J. Duffell 1915-18 (1992).