Following the Norman Conquest, much of the county was subject to the forest laws. To the northwest was the Forest of High Peak under the custodianship of William Peverel and his descendants. The rest of the county was bestowed upon Henry de Ferrers, a part of it becoming Duffield Frith. In time the whole area was given to the Duchy of Lancaster. Meanwhile, the Forest of East Derbyshire covered the whole county to the east of the River Derwent from the reign of Henry II to that of Edward I.