Marcus grew up in London and after graduating from Worcester College, Oxford with a degree in Physics, he went on to study drama writing with playwright Bernard Kops while supporting himself working in the cloakroom of the Royal Opera House, Covent Garden. His first play Taking Pictures was a winner in the New London Radio Playwright's Festival and was directed by Gerard Murphy. The following year he won BBC Television's Double Exposure screenwriting award for his 60 minute television drama, A Relative Stranger which starred Jason Isaacs, Siobhan Redmond and Ioan Gruffudd. His stage play Dead Certain was produced by Bill Kenwright at the Theatre Royal, Windsor and has gone on to be produced around the world. Marcus's first screenplay Cuckoo won The Oscar Moore Foundation Screenwriting Award and the £10,000 prize was presented to him by Emma Thompson. Since then he has received commissions from Kudos Productions for his original thriller Wake Up Dead and by SQ Productions for an adaptation of Brian Aldiss's cult sci-fi classic NonStop. Other work includes the radio plays Vacant Possession and The True Story Of Mr. Box and the short films Miriam, (directed by Esther Hegarty and based on the short story by Truman Capote) and The Interview (White Dolphin Films)
Marcus is represented by Joe Phillips at Curtis Brown.