As historians believe that before the Norman Conquest there were no more than 400 parish churches in the whole of England, it does on the face of it seem unlikely that Udimore church was one of them.
However, if there was a Saxon church in Udimore, it was probably wholly or partially destroyed in the autumn of 1066. When William sent armed parties out from his fortified base at Hastings, to devastate the countryside and bring back provisions for his men and horses, they were instructed to raid only the towns and villages that lay outside the territory of the Abbey of Fecamp. Within easy range of Hastings and not
owned by Fecamp, Udimore was, therefore, probably a prime target. The sharp decline in its value at this time. and subsequent recovery (as recorded in the Domesday Book) supports this conjecture.

The "church and two acres of meadow" recorded in the Domesday Book 20 years later must refer, therefore, to either an original Saxon church, restored by the Normans, or to a new Norman foundation. The parts of the present structure which experts attribute to the Norman period, seem to date from the early 12th
century, which suggests a second phase of building, some 40 years after the Conquest, forming the nucleus of the church as we know it today. In addition to the nave, which seems to have been about one third shorter than the present nave, there was probably a small semicircular apse, serving as a chancel.

Early in the next century, probably around 1230, a major new building programme was put in hand. The capacity of the nave was augmented by replacing its south wall with an arcade of two arches, beyond which a south aisle was built. At about the same time, the earlier chancel was replaced by a spacious and beautifully proportioned Early English chancel, which has survived, with very few changes, to this day. The brackets of the new chancel arch were decorated with a striking dog-tooth pattern, and the capitals of the two arcade arches were carved with an elegant "stiff leaf design".

Not long after this, both the new aisle and the nave were extended westwards, by the length of one further bay. This naturally involved the construction of a third arcade arch. It was a simpler structure, far less ornate than the other two. This is not surprising, for funds were no doubt scarce then, as they are today, and soon many more resources had to be found for the construction of the tower, the next major project.

Signs of this extension can be clearly seen in the external masonry of the nave North wall, and in the two filled-in doorways nearby. There is an intriguing possible explanation for this. It was customary to locate a north door very near the font.