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".
[1] 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 secured a deal with ICM Partners on the basis of his graduation film, which led to him directing several episodes of the television series Secret Diary of a Call Girl (2007).
[5] He next directed the zombie horror series Dead Set (2008), which was nominated for a BAFTA Television Award for Best Drama Serial.
[5][7] Demange made his directorial film debut with '71 (2014), which stars Jack O'Connell as a soldier deployed to Belfast at the height of political violence in Northern Ireland.