He is said to have been a teacher of Cadoc and to have brought light to the heathens to undo the work of Satan.
William Jenkins Rees, in his book Lives of the Cambro British Saints, describes Tathan as the only son of the Irish King Tathetus.
In preference to succeeding his father as king, Tathan followed the advice of an angel and sailed from Ireland to Britain, taking eight disciples with him.
[3] Tathan was feted by King Caradoc and founded a monastic school at Venta Silurum (Caerwent).
[4] With a donation from Caradoc's son, Ynyr, Tathan then founded a Christian church.