The churchyard also contains the grave of the noted geologists, Edward and Annie Greenly, who pioneered modern geological mapping in Anglesey.

[8] Cristiolus is also credited with the foundation of the church in Eglwyswrw in modern-day Pembrokeshire, south Wales.

[10][11] During the 13th century, the chancel was extended, and the older part of the church may have been rebuilt using the previous stones at this time.

In 1852, restoration work took place to the nave and chancel under Henry Kennedy, architect of the Diocese of Bangor.

[14] People associated with the church include Henry Maurice (elected Lady Margaret Professor of Divinity at the University of Oxford shortly before his death in 1691; his father, Thomas, was the perpetual curate of the church)[15] and the 19th-century writer and priest Owen Wynne Jones (who was the curate for a time in the early 1860s).

[16] The 19th-century Calvinistic Methodist preacher Richard Owen was born in the parish, and is buried in the graveyard that surrounds the church.

[10] One window, in the north wall of the nave, has had stained glass added as a memorial to two local residents who died in the 1990s.

[1] The entrance is through a porch (probably dating from the 16th century) on the south side of the building, at the west end of the nave.

[5] At the west end of the roof, which is made of slate, there is an ornate bellcote for one bell (added by Kennedy).

[10] The nave has a brass memorial to a former Chancellor of Bangor Cathedral, William Morgan (died 1713), his wife and son.

[4] It was given this status on 30 January 1968, and has been listed because it is a medieval church that, unusually for Anglesey, dates substantially from the 12th and 13th centuries.

[3] The 19th-century antiquarian Angharad Llwyd described the church as "a spacious structure, exhibiting some excellent architectural details, and decorated with an east window, of good design, enriched with tracery.

"[21] Writing in 1846 (before Kennedy's restoration work in 1852), the clergyman and antiquarian Harry Longueville Jones noted a wooden gallery at the west end, above the font, inscribed RICHARDUS DE GREY FECIT 1778.

[22] He also said that the chancel arch was "of considerable elegance, unusual in North Wales, having excellent moulding and clustered shafts which have a Middle Pointed character.