St Deiniol was a 6th century Celtic ecclesiastic, traditionally recorded as the first Bishop of Bangor.

Church dedications to the saint are rare, St Deinst's in Llangarron being the only such occurrence in England.

[8] The church contains an early carving, originally thought to be medieval tombstone commemorating a child, but also believed to be Romano-British in date.

[7] The interior, and the churchyard, contain an unusually large number of listed memorials, all designated Grade II.

[40] Other Grade II structures include a sundial which originally formed the tip of the spire and which was removed and reconfigured by Seddon,[41] and three unidentified chest tombs.