Mayes was educated at The Royal School, Armagh and Trinity College, Dublin. He was ordained in 1964 and his first post was as a curate in Portadown after which he spent six years as an USPG missionary in Japan.  He then held incumbencies in Cork and was later Archdeacon of the area before his ordination to the episcopate.
|Church of Ireland titles|
William Gilbert Wilson
| Bishop of Kilmore, Elphin and Ardagh
Kenneth Herbert Clarke
Edward Flewett Darling
| Bishop of Limerick and Killaloe