The Norman Keep at Hedingham castle is one of the finest in the country. It was built around 1140 for Aubrey de Vere II, and was probably designed by William de Corbeuil, Archbishop of Canterbury, who also designed the similar great tower at Rochester Castle. The keep has four storeys, and access is via an entrance on the first floor that was once protected by a forebuilding which has since disappeared, although it is still possible to see where it once joined the tower. The second floor, or banqueting hall, is twice the height of the other floors and has a minstrels gallery in its upper half that runs round the entire room. The room is spanned by the largest Norman arch in the country.

The castle was owned by the de Vere's, Earls of Oxford, until the 17th century. This wealthy and important family created an impressive castle at Hedingham, although it was successfully besieged twice in the early 13th century, first by King John in 1216 and then by the Dauphin of France in 1217. Many improvements were made to the castle during the Tudor period and King Henry VII and Queen Elizabeth I were entertained at Hedingham. But none of these buildings now stand, and the Norman keep is all that remains of the castle, standing alone in the grounds of a mansion house built in the early 18th century.