Stuart is a Consultant Clinical Biochemist and Clinical lead for the Metabolic Biochemistry Laboratory at the University Hospital of Wales. He is also the Director of the Wales Newborn Screening Laboratory and an Honorary Professor in the School of Medicine at Cardiff University. Stuart began his career in Clinical Biochemistry in 1995 at Sheffield Childrens Hospital. He gained his PhD on inherited metabolic disorders in 2000 from the University of Sheffield. From 2000-2003 he was a Research Fellow working in the Wales Heart Research Institute. In 2003, he was appointed as a Paediatric and Metabolic Biochemist in the Department of Medical Biochemistry at the University Hospital of Wales. Stuart completed his training in Clinical Biochemistry and obtained the Fellowship of the Royal College of Pathologists in 2008. In 2018, Stuart was elected as an Honorary Member of the Faculty of Public Health Medicine, Royal College of Physicians.

Stuart has been involved in clinical laboratory service development for over 30 years using a range of analytical technologies and  is actively involved in research aimed at improving the diagnosis of rare diseases. He collaborates with experts from Swansea University and University College London on projects that utilise mass-spectrometry based lipidomic methods to enable earlier diagnosis and intervention for patients with rare diseases.