He took up a post in under Lord Cohen at the Royal Southern Hospital after being demobilised. He also worked at Walton Neurological Unit, Clatterbridge, HM Stanley and Boddelwyddan. Dr Hughes wrote the landmark book An introduction to clinical electro-encephalography (1961) which is used as a textbook and authority on the subject. As his reputation became established, he did a substantial amount of work as a private medico-legal consultant.