Waltheof was the second son of Siward, Earl of Northumbria. His mother was Aelfflaed, daughter of Ealdred, Earl of Bernicia, son of Uhtred, Earl of Northumbria. In 1054, Waltheof's brother, Osbearn, who was much older than he, was killed in battle, making Waltheof his father's heir. Siward himself died in 1055, and Waltheof being far too young to succeed as Earl of Northumbria, King Edward appointed Tostig Godwinson to the earldom. Waltheof was said to be devout and charitable and was probably educated for a monastic life. Around 1065, however, he became an earl, governing Northamptonshire and Huntingdonshire. Following the Battle of Hastings he submitted to William and was allowed to keep his pre-Conquest title and possessions. He remained at William's court until 1068.
First revolt
When Sweyn II invaded Northern England in 1069, Waltheof and Edgar Aetheling joined the Danes and took part in the attack on York. He would again make a fresh submission to William after the departure of the invaders in 1070. He was restored to his earldom, and went on to marry William's niece, Judith of Lens. In 1072, he was appointed Earl of Northampton. The Domesday Book mentions Waltheof : "'In Hallam, one manor with its sixteen hamlets, there are twenty-nine carucates to be taxed. There Earl Waltheof had an "Aula" . There may have been about twenty ploughs. This land Roger de Busli holds of the Countess Judith." In 1072, William expelled Gospatric from the earldom of Northumbria. Gospatric was Waltheof's cousin and had taken part in the attack on York with him, but like Waltheof, had been pardoned by William. Gospatric fled into exile and William appointed Waltheof as the new earl. Construction of Durham Castle began under Waltheof in 1072 after receiving orders to commence this project from William. The castle would be significantly expanded by Bishop William Walcher and his successors in later years. Waltheof had many enemies in the north. Amongst them were members of a family who had killed Waltheof's maternal great-grandfather, Uchtred the Bold, and his grandfather Ealdred. This was part of a long-running blood feud. In 1074, Waltheof moved against the family by sending his retainers to ambush them, succeeding in killing the two eldest of four brothers.
Second revolt and death
In 1075 Waltheof joined the Revolt of the Earls against William. His motives for taking part in the revolt are unclear, as is the depth of his involvement. However he repented, confessing his guilt first to Archbishop Lanfranc and then in person to William, who was at the time in Normandy. He returned to England with William but was arrested, brought twice before the king's court and sentenced to death. He spent almost a year in confinement before being beheaded on 31 May 1076 at St. Giles's Hill, near Winchester. He was said to have spent the months of his captivity in prayer and fasting. Many people believed in his innocence and were surprised when the execution was carried out. His body was initially thrown into a ditch, but was later retrieved and buried in the chapter house of Crowland Abbey in Lincolnshire.
Cult of martyrdom
In 1092, after a fire in the chapter house, the abbot had Waltheof's body moved to a prominent place in the abbey church. When the coffin was opened, it is reported that the corpse was found to be intact with the severed head re-joined to the trunk. This was regarded as a miracle, and the abbey, which had a financial interest in the matter began to publicise it. As a result, pilgrims began to visit Waltheof's tomb. He was commemorated on 31 August. After a few years healing miracles were reputed to occur in the vicinity of Waltheof's tomb, often involving the restoration of the pilgrim's lost sight. They are described in the Miracula Sancti Waldevi. Waltheof's life thus became the subject of popular media, heroic but inaccurate accounts being preserved in the Vita et Passio Waldevi comitis, a Middle EnglishWaltheof saga, since lost, and the Anglo-Norman Waldef.
