Llanddewibrefi 1 dates from the sixth century. It was first noted in 1796, when it reportedly stood in the side of the churchyard's south-east stile. The stone is set against the north side of the chancel arch inside the church. In 1925 it was standing against the church's external east wall.

The stone is an unshaped rectangular pillar, inscribed with two uneven lines of Latin which read vertically downwards. The inscription has been translated as '(D)ALLVS/Dvmelvs' meaning 'Blind Unlucky'. The top of the stone has broken off, which has damaged the first letter of each line.

Sources include:
Edwards, N. 2007, A Corpus of Early Medieval Inscribed Stones and Stone Sculpture in Wales: Volume II South-West Wales

N Vousden, RCAHMW, 3 December 2013