Hereward the Wake (c. 1035 - 1072), known in his own times as Hereward the Outlaw or Hereward the Exile, was an 11th-century Anglo-Saxon leader involved in resistance to the Norman conquest of England. According to legend, Hereward's base was in the Isle of Ely, and he roamed the Fens that surround what is now Lincolnshire, leading popular opposition to William the Conqueror. The name Hereward is composed of Old English roots here = army, and weard = guard , and is cognate with Old High German Heriwart and modern German Heerwart. The title "the Wake" was popularly assigned to him many years after his death.
Hereward's birth is conventionally dated as 1035/6 because the Gesta Herewardi indicates that he was first exiled in 1054 at the age of 18. However, since the account in the Gesta of the early part of his exile (in Northumberland, Scotland, Cornwall and Ireland) appears to be largely fictitious, it is hard to know if we can trust this. Peter Rex, in his 2005 biography of Hereward, points out that the campaigns he is supposed to have fought on in Flanders seem to have begun around 1063, and suggests that Hereward in fact went to Flanders - meaning that, if he was 18 at the time of his exile, he was born in 1044/5.
Partly because of the sketchiness of evidence for his existence, his life has become a magnet for speculators and amateur scholars. The earliest references to his parentage make him the son of Edith and Leofric of Bourne. Alternatively, it has also been argued that Leofric, Earl of Mercia and his wife Lady Godiva were Hereward's real parents. There is no evidence for this - and Abbot Brand of Peterborough, stated to have been Hereward's uncle, does not appear to have been related to either Leofric or Godiva. Some modern research suggests him to have been Anglo-Danish with a Danish father, Asketil: since Brand is also a Danish name it makes sense that the Abbot may have been Asketil's brother.
His place of birth is supposed to be in or near Bourne in Lincolnshire. It is claimed that he was a tenant of Peterborough Abbey, from there he held lands in the parishes of Witham on the Hill and Barholm with Stow in the south-western corner of Lincolnshire, and of Croyland Abbey at Crowland, eight miles east of Market Deeping in the neighbouring fenland. In those times it used to be a boggy and marshy area. Since the holdings of abbeys could be widely dispersed across parishes, the precise location of his personal holdings are uncertain, but were certainly somewhere in south Lincolnshire.
It is thought that he had already rebelled against Edward the Confessor before 1066, whom he saw as already aligning England with the Normans, and that he was declared an outlaw as a result. It has been suggested that, at the time of the Norman invasion of England, he was in exile in Europe, working as a successful mercenary for the Count of Flanders, Baldwin V, and that he then returned to England.
In 1069 or 1070 the Danish king Swein Estrithson sent a small army to try to establish a camp on the Isle of Ely. They were joined by many, including Hereward. His first act was to storm and sack Peterborough Abbey in 1070, in company with local men and Swein's Danes:  his justification is said to have been that he wished to save the Abbey's treasures and relics from the Normans.
In 1071 he and many others made a desperate stand on the Isle of Ely against the Conqueror's rule. Some say that the Normans made a frontal assault, aided by a huge mile-long timber causeway, but that this sank under the weight of armour and horses. It is said that the Normans, probably led by one of William's knights named Belasius (Belsar), then bribed the monks of the island to reveal a safe route across the marshes, resulting in Ely's capture. Hereward is said to have escaped with some of his followers into the wild fenland, and to have continued his resistance.
Details of Hereward's life after the fall of Ely are as inconclusive as most of his life prior to the siege. The 12th century chronicle, Gesta Herewardi, (of unknown authorship: first published by Thomas Wright in 1839 and translated by W. Sweeting for the 1895 edition), says Hereward was eventually pardoned by William and lived the rest of his life in relative peace. Geoffrey Gaimar, in his Estoire des Angleis puts a slightly different slant on things, he suggests that after his pardon he moved to France where he was murdered by a group of Normans. The other possibility is Hereward received no such pardon and went into exile never to be heard from again, as this was the fate of a lot of prominent English men after the Conquest it is a distinct possibility. 
The epithet "the Wake" is first attested in the late fourteenth-century Chronicon Angliae Petriburgense, ascribed by its first editor J. Sparke to the otherwise unknown John of Peterborough. There are two main theories as to the origin of the tag. Popular legend interprets it as meaning "the watchful", and supposes that Hereward acquired it when, with the help of his servant Martin Lightfoot, he foiled an assassination attempt during a hunting party by a group of knights jealous of his popularity. However, it appears more likely that the name was given to him by the Wake family, the Norman landowners who gained Hereward's land in Bourne (Lincolnshire) after his death, in order to imply a family connection and therefore legitimise their claim to the land.