This study is based on the fact that hagiographical texts can be used as historical sources. It examines texts produced at St Albans Abbey in the second half of the twelfth century which record the lives and miracles of St Alban and St Amphibalus, some of which were written by the monk William of St Albans. These texts were a stage in the development of the legend of St Alban which had its origins in Roman Britain. Textual and historical evidence suggests that they were written to provide both literary back-up for the discovery of the relics of St Amphibalus in June 1177, at Redbourn, near St Albans, and to document the emergent cult of that saint. The text can also be used to show that a principal motive for the initiation of the cult of St Amphibalus was the success of the cult of St Thomas of Canterbury, although there is also other evidence to suggest that St Albans Abbey was in debt and needed a new source of income. The invention-account and the miracle-account of St Amphibalus have not been studied before, and provide much information about the mechanics of cult-initiation and the spread of a 'new' saint's reputation for healing power