Christopher joined the Department of International Politics in January 2019, having previously taught History at the University of Huddersfield and Leeds Trinity University. He was awarded a PhD in History - for his thesis entitled 'Managing Armageddon: the science of transportation and the British Expeditionary Force, 1900-1918' in 2015. His thesis was subsequently awarded the Donald Coleman prize for the best doctoral dissertation in the field of business history by the Association of Business Historians in May 2016.

Christopher currently teaches on both undergraduate and postgraduate modules within the Department of International Politics, and his interests cover the evolution of warfare in the modern era, the public image of the British Army, and modern strategy. His research focuses on the intersections between the state, the military, and private enterprise, the influence of logistics on military operations, and the development of professional military education. He has produced material for a range of scholarly and popular publications, acted as an academic consultant on the BBC2 series Railways of the Great War, and was a founding member of the First World War Network, an AHRC-funded hub for postgraduate students and early career researchers interested in any aspect of the First World War. He is currently establishing a new centre of expertise in the study of coalition warfare under the heading 'Not enemies, but friends? Coalition warfare, past, present, and future'. 

Christopher's first monograph, entitled Civilian Specialists at War: Britain's Transport Experts and the First World War was published in April 2020 by the University of London Press as part of the New Historical Perspectives series. It is available as a free download from the Humanities Digital Library.

Christopher is currently the Director of Undergraduate Studies within the Department, responsible for overseeing the strategic development of the learning and teaching environment and coordinating undergraduate provision. He is also the department's representative on the university-wide Equality Champions committee.

He previously acted as Deputy Director of Undergraduate Studies within the department between September 2019 and August 2021. In this role he was responsible for chairing the undergraduate examination boards and overseeing the department's adherence to University Special Circumstances policy.