Powis joined the Royal Free London NHS Foundation Trust in 1997 as a consultant, becoming the trust's medical director in 2006 and chief clinical information officer in 2016. He left the Royal Free at the end of 2017 to become medical director of NHS England, a post he took up at the beginning of 2018. During this time, Powis was involved in a partnership for the Royal Free to share information with Google Deepmind.[8] His main clinical interest is renal transplantation.[9]
He is a past non-executive director of North Middlesex University Hospital NHS Trust (including a period of eight months as acting chairman), chair of the Association of UK Hospitals medical directors' group, and chairman of the Joint Royal Colleges of Physicians Training Board speciality advisory committee for renal medicine.[1] He sat on the board of Medical Education England.[1]
Powis sponsored the National Medical Director's Clinical Fellow scheme, established in 2011 and run by the Faculty of Medical Leadership and Management. The scheme provides doctors in training with a unique opportunity to spend 12 months in national healthcare-affiliated organisations outside of clinical practice to develop their skills in leadership, management, strategy, project management and health policy.[10]
During the COVID-19 pandemic, which began in the spring of 2020, he frequently spoke as part of the government's team for daily briefings.[11] He was a member of the Scientific Advisory Group for Emergencies (SAGE) and advised senior ministers within HM Government throughout the pandemic.[12]