The Reverend William James Davies was the first Vicar of Ystalyfera, from 1903 to 1912. Until 1903 Ystalyfera was part of the Parish of Llanguicke and was administered by Assistant Curates. With the construction of Saint David's Church in 1890-1891, Ystalyfera now had two Church of England churches, but remained part of the Parish of Llanguick. In 1903, Ystalyfera became a parish in its own right, with one vicar covering both Saint David's and Holy Trinity. It was decided that services at Saint David's would be in English, and those in Holy Trinity in Welsh only.