The decision was condemned at the time by Harry Longueville Jones, a clergyman and antiquarian, who lamented the "melancholy fate" of what he called "one of the largest and most important [churches] in the island of Anglesey".

[3] In the 12th century, Gerald of Wales said that the church possessed a curious stone carving similar to a thigh that would always return by the next day no matter how far away it was taken.

A Norman earl, he recounted, had chained it to a large rock and thrown it into the sea, only for the stone to return to the church by the following morning.

A sandstone chest containing bone fragments, possibly are relics of a saint, were found buried beneath the altar.

[3] As a result, writes the historian Antony Carr, the reason for the "distant community" of Augustinians in Beddgelert possessing Llanidan and three other churches in Anglesey cannot now be discovered.

His successor, Elizabeth I, granted the advowson (the right of a patron to choose the parish priest) and the grounds surrounding St Nidan's, including the estate house called Plas Llanidan, to an Edward Downam and a Peter Ashton; thereafter, in the following centuries, the right and the land passed on through sale, on marriage and by bequest into the hands of the Boston family.

[9] The remaining part of the south nave, the oldest section of the present structure, dates from medieval times; the north doorway and tracery (patterns of stonework in the windows) point to the 14th century.

[4][13] The 19th-century clergyman and antiquarian Harry Longueville Jones disputed the need to replace the old church and condemned its "melancholy fate", describing the reasons for its demise as "pretexts".

[1] He stated that "when buildings, dedicated to God's service by the piety of former ages, are allowed to be treated in this manner by the constituted authorities of the land ... the institutions to which they are attached cannot be expected to find greater favour at the hands of the fickle and ignorant multitude.

[1] The cleric and antiquarian Henry Rowlands, who wrote a history of Anglesey entitled Mona Antiqua Restaurata, was the vicar of St Nidan's from 1696 until his death in 1723.

[5][14] Thomas Williams, a politician and businessman who became wealthy through copper mining in Anglesey, was buried in the churchyard in 1802, but was reburied at St Tegfan's, Llandegfan, in the 1830s.

The western wall has been rebuilt and buttresses added to the south side and north-west corner to help support the structure;[3] Jones thought that they dated from the 16th century.

[3] The 19th-century antiquarian Angharad Llwyd, who wrote a history of Anglesey in 1833, recorded the story noted by Gerald of Wales in the late 12th century that the church once possessed a stone "resembling a human thigh" which would return "of its own accord" however far away it was carried.

It was popularly believed that if a couple had sexual intercourse near the stone (something that Gerald said happened "frequently"), it would "sweat large drops of water" and the woman would not become pregnant.

[17][18] When Rowlands was vicar of St Nidan's, a small chest was found buried about 2 feet (60 cm) under the altar, containing some bone pieces.

[2] It was given this status on 30 January 1968 and has been listed because it is regarded as "a good example of a simple medieval rural church, enriched by 15th-century additions.

"[3] Cadw, the Welsh Government body responsible for the built heritage of Wales and the inclusion of Welsh buildings on the statutory lists, also notes that although it was partly demolished in the middle of the 19th century, "what remains can be considered a well preserved and important survival of a double-naved church, retaining many 15th-century features such as the central arcade.

[21] In 1802 the clergyman and antiquarian John Skinner visited Anglesey to see the island's Celtic remains, beginning his tour by rowing across the Menai Strait to land at Llanidan.

[1] He noted the "rather curious" position of the church, in a "nearly circular enclosure" with tall trees around it, and said that "the effect of the western end with the porch, overgrown by an enormous quantity of ivy, was picturesque in the extreme".

"[23] At the time he saw it, the walls were still largely in place but the only roofed section was the western end; he commented that most of the church was "open to the skies.

[24] The authors of a 1990 book about the lost churches of Wales said that St Nidan's was "now an evocative shell decorously mantled with ivy and enclosed by an overgrown graveyard".