His first taste of film-making in Britain was acting in Peter Watkins' The War Game (he had the role of the jumpy GI who triggers the nuclear strike).
He worked for a time as a producer/director for BBC Panorama, making programmes on Ronald Reagan, then governor of California; the May 1968 events in Paris, and censorship.
The success of that campaign led him to join John Ellis (media academic) and Keith Griffiths in founding the production company Large Door Ltd.
Just before his death, Hartog completed Beyond Citizen Kane, his film on the development of TV in Brazil, concentrating on the role of Rede Globo, the largest media conglomerate in the country.
The documentary is critical of the company's ties to the military dictatorship and likened the conglomerate's leader, Roberto Marinho, to the Citizen Kane figure of the 1941 American film for manipulation of news.
[1] During its development, Hartog had made signed agreements with various cultural and political groups in Brazil to give them the non-TV rights, in order to provide for wide distribution in the country.
He was a perennial outsider who spent most of his life dreaming up alternatives to the mainstream orthodoxies, but nonetheless took a serious academic interest in the political and economic structures of the film industry.
He was also one of the very few British film-makers with an informed and passionate commitment to non-British cinemas, especially those of Africa, the Middle East and South America.