The south doorway is the only major carved work of the Romanesque building still in its 12thc. position, but several loose Romanesque carved stones also remain, these kept in the E end of the church and in the on-site museum. What appears to have originally been a two-cell church was rebuilt in 1579 and has extensive later additions on the N and S sides. In 1851, the Rev’d John Sime drew a plan of the church as it existed at that time. In 1893, the church was extended at the W end and a new aisle was built along the N side of the nave, at which time the so-called ‘Duddingston Aisle’ on the N side of the nave was taken down.

Bede, writing in the first half of the 8thc., states that Abercorn (Aebbercurnig) had been an important early religious site. He writes that in 684 Bishop Trumwine had to leave the abbey of Abercorn, which had been in the territory held by the English, in order to avoid the advances of the Picts. Bede also seems to infer that the monastery was still in existence at the time he was writing, saying that traces of the Roman wall (i.e. the Antonine Wall) could still be seen ‘to this day’ (usque hodie) and that it started west of the monastery of Abercorn. Carved stonework from as early as the later-7thc. or early-8thc. has been found in and around Abercorn, confirming the antiquity of the site. In the early-12thc. Symeon of Durham mentions Abercorn (Eoriercorn) in a list of places under the year 854 in reference to the diocese of Lindisfarne. It is unknown when the monastery ceased to exist and documents do not refer to the church at Abercorn again until 1173, when Richard Bishop of Dunkeld released (liberavit) the church of Abercorn from the patronage of a John Avenel (Mylne, p. 6). The Bagimond Roll of the later 13th century lists Abercorn as a vicarage (vicarius). There was formerly a castle on an adjoining piece of land, separated from the church land by the Cornie rivulet, excavations of which uncovered evidence for a building (or buildings) of medieval date. Although there is no specific record of who first owned the land at Abercorn in the 12thc., it is thought by many that Robert Avenel is likely to have been given the land by King David I. Robert appears in records from at least the early 1140s and continued to appear in documents until his death in 1185. Myne does not state the family relationships of the John Avenel mentioned for 1174, but Robert had a grandson named John by his son and heir Gervase. In about 1236-to-1249, Abraham vicar of Abercorn appears as a witness to a charter made by John Avenel, son of Gervase (Inchcolm Charters, p. 15). Abercorn passed by marriage to the Grahams, then to the Mure/More family, eventually passing to the Lyndseys. In a charter of 1315, John de Graham is called lord of Abercorn (Morton Registrum, vol. 2 p. 14). In a later charter of 1370-76, in which William More confirms an earlier charter of John Avenel, William is titled lord of Abercorn. In the same charter, the Barony of Abercorn is mentioned, as is also Gervase Avenel (Inchcolm Charters, p. 37 no. XXXVIII). John, 8th Lord Lyndsey of the Byres resigned the Barony of Abercorn to King James VI of Scotland. In 1603 the king granted the barony to James Hamilton, who was created 1st Earl of Abercorn. Ecclesiastically, Abercorn became part of the so-called Barony of Aberlady during King James II of Scotland’s reign (1437-60). This part of the diocese of Dunkeld consisted of the group of churches and lands S of the River Forth.

In the Corpus of Scottish Medieval Parish Churches, the proposed date of the S doorway is given as about the 2nd quarter of the 12thc. Elsewhere, it is sometimes suggested as mid-12thc.

Only one other carved tympanum survives in Scotland, at Linton in Roxburghshire, but the carved work on the two is unrelated. The nested-lozenge decoration at Abercorn can be compared nearby at the churches of Duddingston (Edinburgh) on a shaft of the S doorway and at Dunfermline Abbey (Fife) on a loose section of shaft.

MacKinlay gives the dedication of the 12thc. church as St Wilfrid, but evidence for this in the 12th cent. and later is lacking.

Crawford suggests an 11thc. or early-12thc. for the three coped grave covers. Lang, more recently, proposes that coped grave cover (A) was carved in the 11thc., grave cover (B) in the early 12thc., and grave fragment (C) in the 12thc.

Reid thought that the arm-/foot-like motif on the flat grave cover might have been added at a later date. There is, though, no certainty for this. The grave cover is unlikely to be before the very late-12thc. and could be later.

Information concerning where and how the small loose base was found is illusive. Comparisons for this, with its simple torus roll, are not forthcoming. The date, therefore, is not at present certain.

Comparisons for the larger base stones are widespread and found frequently in the later-12thc. Similar bases in the N of Britain, for example, include Durham Cath. (Galilee), Jedburgh Abbey (nave), St Andrews Cath. (E end), Kelso Abbey, Furness Abbey, and Holm Cultrum Abbey.

Robert Avenel and his family appear to have been quite close to the Scottish royal family. Not only was Robert a Justicier for part of King William I of Scotland's reign, but one of his daughters became a mistress to the king and bore a daughter by him, named Isabel, who the king later gave in marriage to Robert de Brus. Gervase, son of Robert Avenel, also served as Justicier under King William I. Robert, Gervase and Roger (a son of Gervase) were buried at the Cistercian abbey at Melrose.

George Chalmers, in his Caledonian, appears to be the source of unsupported information concerning the first-known owners of Abercorn in the 12th century, stating that it was the Grahams. He has been repeated by various people, but Lawrie (p. 32 note) noted this as an error. It appears that there are no known early documents which uphold Chalmers' assertions on this point.