Professor Warner became a qualified medical practitioner in 1987 and gained his clinical education at the University of Oxford School of Medicine, he obtained his MRCP in 1990 and FRCP in 2002. He was appointed a lecturer in neurogenetics at the Institute of Neurology and obtained his PhD at the University of London.
In 2011 he was promoted to professor of Clinical Neuroscience at Institute of Neurology, UCL. He serves on the scientific advisory committee and has served on the editorial board for the movement disorders Journal. He was also involved in developed the multidisciplinary Huntington's disease clinic at national hospital for neurology and neurosurgery which received an NHS good practice award in 2005.