Rhys joined Newcastle University in 2017 where he is a Reader in Epilepsy, his work focuses on the causes and consequences of epilepsy. He has a long established working relationship with SUDEP Action, publishing on the Epilepsy Deaths Register with the charity. He has a number of representative roles, chief of which is being he current President of the British branch of the International League Against Epilepsy.

He is also an Honorary Consultant in Epilepsy at the Royal Victoria Infirmary, where he runs a busy epilepsy practice that includes a large epilepsy and intellectual disability clinic, with a particular focus on rare genetic epilepsies. He is also a Consultant in the NHS Highly Specialised Service for rare mitochondrial disorders, where his interests include epilepsy and stroke-like episodes. Rhys is the Research Lead for Neurosciences and the Chief Investigator for several epilepsy drug studies across the UK, as well as overseeing neurotechnology studies in Newcastle.