His series Guantanamo: If the Light Goes Out (2010), Letters to Omar (2010), and Control Order House (2012) engage with state censorship to explore hidden experiences and spaces of control and incarceration in the global ‘war on terror.’ His work The Mountains of Majeed (2014) reflects on the end of Operation Enduring Freedom in Afghanistan, the longest war in American history. Clark has received worldwide recognition for his work, including the Royal Photographic Society Hood Medal for outstanding photography for public service and the British Journal of Photography International Photography Award, as well as being shortlisted for the Prix Pictet and the W. Eugene Smith Award. His work has been acquired for public collections in Europe and America. He teaches at the University of the Arts, London.