Mat is the Chief Executive of the Great Ormond Street Hospital for Children, having previously been GOSH's Medical Director. Before joining GOSH, Mat was a Medical Director in BUPA Health Services as well as Medical Director, Deputy Chief Executive, and Transformation Director of the Royal Orthopaedic Hospital. Mat is a consultant spinal surgeon, and he participated in Ride for their Lives 2021, cycling as a part of the core group which went the whole way from London to Glasgow for COP26.