Bloom's first novel was Episode (1956), which was later retitled Transvaal Episode. This book, an account of an uprising in the fictional township of Nelstroom in the aftermath of the 1952–3 African National Congress defiance campaign, was banned by the South African government for being dangerous to the safety of the apartheid state. The novel won the British Authors' Club Prize for the best novel of 1956, but Bloom was denied an exit permit to travel to England to receive the prize. Bloom worked with and was jailed next to Nelson Mandela. Richard Attenborough was very impressed with this work, and had been interested in adapting Transvaal Episode into a film; he opted to do Cry Freedom instead.
Bloom wrote his second novel, Whittaker's Wife (1962) while he was serving a three-month detention in prison. He also wrote the play for the musical King Kong: An African Jazz Opera (1961), a tragedy of a black boxer from the ghetto, which reached a multiracial audience both locally and internationally.
In 1963, he was deported to England. In 1965, he became a Professor of Law at the University of Kent, England, where he worked until 1974. He married Sonia Copeland, who had two children, Samantha Bloom and actor Orlando Bloom. Nine years after Harry's death, Sonia revealed to her children that their biological father was family friend, Colin Stone.
Harry Bloom died of a stroke in 1981 at the age of 68.