It is reputed to house the grave of Seregri, an Irish warrior who lived in the area in the 5th century.

Eglwys y Bedd is a medieval building in the south-west corner of the churchyard of St Cybi's, Holyhead (the principal port in Anglesey, north Wales).

[3] It was in ruins before 1748, when Thomas Ellis, the rector of St Cybi's, restored the nave for use as the first school in Holyhead.

He was the leader of a group of Irish warriors who had settled on Anglesey and who were driven out by the Welsh ruler Cadwallon Lawhir ap Einion.

[2] The antiquarian Angharad Llwyd, writing in 1833, reported that when the ruins of Eglwys y Bedd were removed, a stone coffin "containing human bones of a prodigious size" was found at the north side of the chapel where Seregri was reportedly buried.