My story about Hereward is fictional. However, it is generally accepted that he existed and fought against King William of Normandy, because the Normans killed many English people and took their properties for themselves when William became King of England in 1066.
Hereward spent much of his time hiding in the Fens and launching attacks on William's men, and was often in disguise. It would have been very difficult for people to write historical accounts because many of them could not read or write and probably never even saw him. Some of the monasteries kept records but only a few survived. It would be impossible to tell whether they were accurate because they were written so long ago. Nevertheless, the few stories which exist about Hereward are fascinating to read and he certainly sounds like a true hero.