The nave is a small one, measuring 33ft x 13ft. The narrow width of the north and east walls and their height suggests that they are Saxon. This was borne out by the nature of the fabric revealed over the chancel arch during repairs in 1999. It is possible that the west end of the nave was extended before the present tower was built. The west wall is thicker and there is a possible change ofbuild visible at foundation level in the external drainage gully along the north wall, about seven feet west of the porch. (This wall was rendered externally in 1974.) Thus, the nave may originally have been similar to the Saxon church at Bradford on Avon (25ft 2ins x 13ft 2ins).
Plaster was stripped from the wall above the chancel arch, exposing irregular rubble consisting of large weathered lumps of field stone randomly laid in loam. This type of construction and its narrow width (2ft 6ins) further indicates that the wall is Saxon. Packing stones were clearly visible round the chancel arch which was probably inserted in the lSth century. A time capsule containing a recent photograph of the church and one from the early 20th century was placed in the wall before it was replastered.
The ancient pulpit is a perfect example of a 15th century wall pulpit. It was probably in use until 1787 , when the wooden pulpit was bought and placed in the chancel. The Church Rambler published in 1876 records that in 1849 it suffered further ignominy when 'a heating apparatus was introduced in the form of a common stove, placed in the stone pulpit and the pipe carried along the north side, across the gallery and out of a window on the south' .The stove had been removed by 1876.
The display of Royal Arms in churches was compulsory after the Restoration. St Mary's Royal Arms on the north wall was painted by Charles Field of Trowbridge in 1771 at a cost of £8 18s 6d. He was a house painter by trade, which may account for the unusual animation of the lion and the unicorn and the more lifelike depiction of the rose and thistle than the normal heraldic varieties. The door beneath the Royal Arms in the north wall dates from the 15th century.