One look at the building and you realize that the nave is actually smaller than the chancel. This oddity is explained by the fact that the west tower collapsed in the 18th century, at which point the nave was considerably shortened.
The best feature of the church is the Norman west door, which architectural historian Nickolaus Pevsner called one of the finest in England. The door is not original to St Mary's; it came from All Saints church, also in Barton Bendish parish, when that latter church was demolished around 1780. The door was needed to help repair the nave at St Mary's following the collapse of the tower.
The interior boasts a 14th-century wall painting which may represent St Catherine - the painting shows a wheel with eight spokes and the figure of a woman, so St Catherine is the obvious guess to make. There is a mix of 17th and 18th-century wooden pews.
There is a nicely carved communion table dated 1633, and two very nice wooden carved figures placed high on the east wall.