Duncan is a writer and director. Former Writer in Residence at Paines Plough and the Royal Exchange Theatre, he has written extensively for theatre in addition to working in radio, television and film.
Awards include: UK Theatre Award for Best Director (with Rob Icke for 1984), Best New Play at the Off West End Awards, 2013; the Big Ambition Award, Old Vic 2009; the Pearson Prize, 2008 and runner-up in the JMK Directing Award, 2010. Duncan was also the recipient of two awards in the inaugural Bruntwood Playwriting Competition, 2006 and his work with director Katie Mitchell has been selected for Theatertreffen and the Avignon Festival. Both 1984 and People Places and Things received Olivier Award nominations for Best New Play.
Duncan's new play People, Places and Things finished a sold-out run in the Dorfman space at the National Theatre before transferring to the Wyndhams Theatre in the West End where it will run until June 2016. Paines Plough's production of Every Brilliant Thing finished its run in New York at the Barrow Street Theatre, then toured the UK along with their production of Lungs, before touring Australia and New Zealand. His co-adaptation of George Orwell’s 1984 with Rob Icke for Headlong/Nottingham Playhouse played at the Melbourne Festival in Australia after two runs at Playhouse Theatre in London's West End, and after a US tour it will be returning to the West End in the summer. His play Lungs (Atmen) is playing in rep at Schaubühne in Berlin, directed by Katie Mitchell. The Forbidden Zone is also in rep, directed by Katie Mitchell and will be playing at the Barbican in May 2016.