The first Norman castle was built at Lydford soon after the conquest of 1066; the remains of its earthworks can be seen on the south side of St Petrock's Church. A new tower was built in 1195, slightly north of the original castle, possibly for use as a prison. Sometime in the 13th century it was completely rebuilt. A ditch was dug around the tower and the soil piled up against the ground floor to form a mound. The top two floors were converted into a small keep, while the ground floor was filled in. At the same time the earthwork bailey to the northwest was constructed. By the early 18th century the castle had become derelict, but it was repaired, and for the next century served as a jail and courthouse, before being abandoned once more and allowed to fall into ruin.