A Romanesque stoup was set against an interior wall of the chapel until the 1950s, when it was moved to the Museum of Scotland, Edinburgh.

The chapel at Herdmanston was founded in the early 13th century by John Sinclair of Herdmanston, appearing in deeds as the ‘chapel of St John the Evangelist near the castle’ of Herdmanston. The chaplain was subject to Salton Church, which belonged to the Abbey of Dryburgh. The abbey was granted a small section of land in return for concessions made for the chapel.

There is no evidence for a church or chapel on this site earlier than the 13th century, yet the stoup is of obvious 12th-century date. The earliest location for the stoup is unknown.