This fragment of wall near St Mary Magdalene’s Church, Hart is the only above-ground remains of a medieval great house owned from the 12th to the 16th centuries by the de Brus and Clifford Lords.

The history is well described in the Scheduled Ancient Monument listing :-

The manor of Hart and Harterness was granted by the king to Robert de Brus
after the Norman Conquest. Documents indicate that the extent of this manor
was larger in pre-Conquest times. Throughout its history, the right of
disposal of the manor was a source of dispute between the Crown and the Bishop
of Durham. The manor subsequently descended through the Brus family most
notably to Robert de Brus VII; after the latter’s assumption to the Scottish
throne in 1306, Edward I granted the manor to Robert de Clifford in whose
family it remained until 1580, with only brief interruption by claims from a
number of bishops. In 1580 the manor was sold to Robert Petrie and John Morley
and then to the Lumley family who, with the exception of a brief period of
administration by Parliament from 1644-1660, retained it until 1770. In 1770
the estate was sold to the Milbank family.