It is barely articulated, rather bluntly supported to the East and South side by large buttresses and simple arched windows later recut. It appears to have had a pulpitum wall between nave (of which only traces of foundations remain) and the choir, of which the archway serves as a West door behind the present communion table. Corbels attached to the Western exterior suggest that this wall has some antiquity, but it does not correspond to a surviving support. The East wall is supported by crude but deep buttresses like those on the South: note how the upper offset is lateral in contrast to the normal forward step below: perhaps this is an example of the transformation of traditional Gothic practice we find in conservative Scottish architecture of the 15th century. [Cf. the Blacadder Aisle of Glasgow Cathedral and King's College Chapel, Aberdeen, with flat-backed tracery] Abandoned by 1679 and brought back into use from 1749, the orientation of the church was reversed and a Gothic window, entrance and gallery inserted in place of its original East elevation in 1900, with another restoration in 1956.
There is a door into a Sacristy at the NE (a square aumbrey niche at the East end of the North wall survives outside, relating to a doorway to its West inside) and a sedilia and South doorway, notable survivals of the architectural furnishing of a Western Scottish church, though their remarkably primitive headstops, probably 15th-century, are more abstract than most Early Medieval carving. Their capitals, however, have a multi-ring moulded design already found, with the nibbed shaft below, in Northern English and Southern Scottish architecture of the 13th century. The wide shallow chamfer of the South door belies the impression of a Romanesque or Transitional Irish doorway, and might be quite late in date. The large oval eyes of the label headstops are character to the Romanesque corbels of Leuchars, however: either little has changed in the vocabulary available to a Western Scottish carver for 200-300 years, or we are misreading the evidence, for which little objective checking is available. But the head-stops inside are completely square and shield-shaped with hardly any specified eyes; they have been damaged, presumably in the Reformation, however. The steeply pointed North door has a bishop and a nobleman of reasonably natural proportions and expression, but too unstylised to be readily datable between 1250 and 1500. However, the lean face of the bishop can be paralleled in a face in the clerestorey of Sweetheart Abbey, and the sedilia has similar nibbed shafts and capital, in which case they are of late 13th-century date.