In the summer of 1991, shortly before the outbreak of the country's Civil War, he travelled to Algeria to meet his extended family: on this trip he saw "The Battle of Algiers" for the first time, a film in which an aunt of Demange's appeared as one of the film's many non-professional actors. He has said that the awareness of his aunt's role in the film strengthened his love for the medium: "As absurd as it sounds, on some level I think I felt like I had discovered an inheritance to some sort of personal lineage in movies". He began his career at age 18 as a runner on the set of music videos, before enrolling at an arts foundation at the London College of Printing. He later made observational documentaries for General Electric.