Professor Clarke is emeritus professor of clinical neurology at the University of Birmingham, UK. He performed a wide variety of research in Parkinson's disease over the last 40 years including work on the MPTP primate model of the condition, examination of several potential diagnostic tests, systematic reviews of clinical trials in Parkinson's disease, and work on the effects of Parkinson's disease on quality of life and health economics.

Professor Clarke led the teams performing several large pragmatic clinical trials examining medical, surgical and rehabilitation interventions in the condition (PD MED, PD SURG, PD REHAB, PD COMM and PD GEN). He was the clinical advisor to the Technical Team preparing the original 2006 NICE Parkinson's disease guidelines. He was deputy chair of the National Institute for Health’s (NIHR) Efficacy and Mechanisms Evaluation (EME) Board. He was a founding editor of the Cochrane Movement Disorders Group coordinating systematic reviews of health care interventions in all movement disorders.

He is now partially retired focussing on completing the last clinical trials and supporting his patients with mainly Parkinson's disease in clinic. He is otherwise distracted by a large garden and three boisterous grandchildren.