This is from Richard Gough's additions to Camden's 'Britannia' (volume 2):
[Thetford] was a seat of the kings of the East Angles. The Danes are generally supposed to have cast up the great hill [Thetford Castle] here about 865 when they wintered on it opposite to that on which king Edmund's army lay, on the extremity of which are many tumuli (particularly one called the Tut hill) where were buried the slain in the battle between him and them.
Sounds like the Danes still feature in local folklore:
Tutt Hill, Suffolk.
The noises of fighting and a man screaming have been heard over the years. The fighting is said to date from the Viking attack on the town of Thetford which was successfully taken by them. As for the screaming man, tradition tells us that he was a Saxon traitor who betrayed Thetford to the Vikings and was rewarded for his efforts by being executed by his victorious 'allies'.
'They Still Serve: a complete guide to the military ghosts of Britain' by R McKenzie (2008), viewable on Google Books.