The ruined church of St Helen has a two-celled ground plan, with a rectangular chancel narrower than the nave. At one time both the chancel and nave were barrel vaulted. The south nave wall has been thickened on the interior side at some later date, which raises the question as to whether a vault in the nave, at least, was part of the building as first built. Muir, in 1848, wrote that in the nave there were 'indications of a north-west doorway', and that the decoration of the east window consisted of 'a hollow chevron carried round the head and down the sides close to the edges'. He also stated that the chancel arch 'apparently has been of two chevroned orders', that the central capitals were 'double-escalloped', and that the imposts were of 'trigonal form', carved with a double row of chip-carved saltires. The moulding of the jambs of the chancel arch consisted of a larger central half roll, flanked on either side by two smaller rolls. The west wall of the nave has been rebuilt and incorporates several stones carved with chevron. After the Reformation, control of Aldcambus came into the hands of Alexander, Lord Home. By 1556, the church appears to have been in a perilous condition. Sometime after the Reformation the parish of Aldcambus was annexed to that of Cockburnspath and the parish moved to the church there. The uniting of the two parishes was undertaken by the Lords Commissioners of Teinds before 20th May 1610. By 1750, and probably before, the church was in ruin. In 1847, much of the decorated areas of the church remained and were drawn by James Drummond, but large areas were soon afterwards destroyed by someone searching for stone to use for mending other structures. At that time, the land in and around the church had risen considerably and it was not until the early 20thc that the excavations were made to discover various ground-floor level features. Since then, the overgrowth has once again covered most of the surviving carved stones. Amongst the various stones recorded are a number of early coped graves, which are now no longer visible.

Possibly as early as 1095 and certainly by 1098 Edgar (later king) gave the mansionem of Aldcambus (and other places) to the church and monks of St Cuthbert at Durham. This was confirmed in 1100, but in none of the early documents is a church mentioned. Edward of Aldcambus quitclaimed the vill of Aldcambus to Durham in 1198 or shortly after. The first known reference to a church appears c.1200 when Roger, bishop of St Andrews, conferred to the priory of Durham several churches in the diocese of St Andrews, including Aldcambus. Almost immediately following this, the corn tithes were assigned to the monks of Farne Island by Bertram, prior of Durham. Later, R. prior of Durham granted the altar dues of the church of Aldcambus, except for a teind of corn, to William of Mitford. Other revenues from Aldcambus were passed to Coldingham Priory in the late 14th or early 15thc, by which time the church appears to have been placed in their possession. In a petition by John, prior of Coldingham, mention is made that no vicar was residing at Aldcambus and that divine worship there had been almost entirely abandoned. Coldingham Priory separated from Durham’s superiority in 1462 and Aldcambus remained attached to it until the Reformation. A hospital at Aldcambus is also referred to c.1213. In the time of William the Lion (1165-1214), David de Quniwood, baron of Quinwood, endowed the hospital by giving to it and the lepers there a half poughgate of land at Alcambus, formerly held by Ralph the Tanner.

The church of Old Cambus appears to be early 12thc, probably no earlier than c.1120 because of the use of chevron. There is no record of an earlier church, nor have the foundations of one been found. The series of chevron blocks re-used in the west wall can only have been part of a larger arch, judging from the slight curve of the sides. This might lead one to think that they come from the chancel arch, but as there is no noticeable curve of the chevron, itself, it must be left open to debate as to where these stones were originally used. Amongst several grave covers, two have been found that resemble late 'hogback' monuments. Lang (1975) suggested an 11thc date for both of these, but it is possible they are a bit later and contemporary with the early parts of the present ruined church.