He was the son of Samuel and Kate Louise Mann and went on to be educated at Moreland State School and Wesley College.
[1] After the failure of his father's drapery business in 1913 he left his studies and worked as a clerk in the Public Service before joining up with the AIF during World War I. Mann served on the Western Front before being repatriated back to Britain in 1919 and then returning to Australia.
[1] Back in Victoria he resumed his studies at the University of Melbourne, completing a Law degree before marrying Florence Eileen Archer in January 1926.
[1] He enrolled in the Victorian Bar and began writing poetry and fiction, which resulted in the publication of his first novel, Flesh in Armour, in 1932.
[1] During World War II he worked with the Aircraft Production Commission, following which he returned to the Public Service.