Halstow was considered to be a holy place (‘Heiligestowe’) from the 6th century, and a document dating from the 11th century, the time of William the Conqueror, refers to the church in ‘Halgastow’. However, it is thought that the altar and choir area of the church, the chancel, may date from the early 9th century, having replaced an existing wooden Saxon church. The first recorded parish priest is John de London, nephew of Thomas Becket.
Roman tiles can be seen in the construction, especially in the oldest part of the outer walls. As the church was extended in the 12th to 14th centuries, the supply of Roman tiles gave out. The large lead font near the organ dates from the 12th century, and is one of only some thirty in the country still in use.
The East window above the altar was installed in the early 1920’s by the then vicar, the Revd Edward Olive. Showing Christ coming to a soldier in the trenches, it follows a design by the vicar’s nephew by marriage, Brigadier Roland Bradford, youngest brigadier in the British army in World War I. Bradford had intended to distribute the picture to his men at Christmas 1917, a plan cut short by his death at the front. It was the Revd Olive’s wife who discovered the ancient font, which had been covered in plaster some centuries before, perhaps to hide it.