Waltheof, was the younger son of Earl Siward of Northumbria. In 1065 he became Earl of Huntingdon. After the Battle of Hastings he submitted to William the Conqueror and he was allowed to keep his estates.
In 1072 Waltheof became Earl of Northumbria. William also arranged for him to marry his niece Judith. This strategy did not work and in 1075 he joined a revolt led by Ralph, Earl of Norfolk and Roger, Earl of Hereford. Waltheof was captured and was executed on 31st May 1076. Waltheof was the only prominent Englishman to be executed in William's reign.