The Brigantes were the major Celtic tribe in what is now Northern England. With a stronghold at the sandstone outcrop on which Manchester Cathedral now stands, opposite Salford’s original centre, their territory extended across the fertile lowland by the River Irwell that is now Salford and Stretford. Following the Roman conquest of Britain, General Agricola ordered the construction of a Roman fort named Mamucium (Manchester) to protect the routes to Deva Victrix (Chester) and Eboracum (York) from the Brigantes. Salford was founded when the fort was completed in AD 79, and for over 300 years the Pax Romana brought peace to the area. Both the main Roman road to the north, from Mamucium to Ribchester, and a second road to the west, ran through what is now Salford, but few Roman artefacts have been found in the area. The withdrawal of the Romans in AD 410 left the inhabitants at the mercy of the Saxons. The Danes later conquered the area and absorbed what was left of the Brigantes. Angles settled in the region during the Early Middle Ages and gave the locality the name Sealhford, meaning “ford by the willows”. According to the Anglo-Saxon Chronicle, Sealhford was part of the Kingdom of Northumbria until it was conquered in 923 by Edward the Elder. Following the emergence of the united Kingdom of England, Salford became a caput or central manor within a broad rural area in part held by the Kings of England, including Edward the Confessor. The area between the rivers Mersey and Ribble was divided into six smaller districts, referred to as “wapentakes”, or hundreds. The south east district became known as the Hundred of Salford, a division of land administered from Salford for military and judicial purposes. It contained nine large parishes, smaller parts of two others, and the township of Aspull in the parish of Wigan. After the defeat of the Harold II during the Norman conquest of England, William I granted the Hundred of Salford to Roger the Poitevin, and in the Domesday Book of 1086 the Hundred of Salford was recorded as covering an area of 350 square miles (906 km2) with a population of 35,000. Poitevin created the subordinate Manor of Manchester out of the hundred, which has since in local government been separate from Salford. Poitevin forfeited the manor in 1102 when he was defeated in a failed rebellion attempt against Henry I. In around 1115, for their support during the rebellion, Henry I placed the Hundred of Salford under the control of the Earldom of Lancaster, and it is from this exchange that the Hundred of Salford became a royal manor. The Lord of the Manor was either the English monarch, or a feudal land owner who administered the manor for the king. During the reign of Henry II the Royal Manor of Salford passed to Ranulf de Gernon, 4th Earl of Chester.