A school caretaker in the Cambridgeshire commuter town, Huntley committed one of the most shocking child murders of the century.
Holly Wells and Jessica Chapman had been at a family barbecue in August 2002. It’s believed they were on their way to buy sweets when Huntley, then aged 28, lured them back to his home and killed them.
The BBC understands that triple killer Anthony Russell, 43, is suspected of attacking Huntley.
Having been kept on life support in hospital, it was turned off on Friday, according to prison sources.
This was not the first time he had been attacked at HMP Frankland. In 2010, he was slashed across the throat and needed 21 stitches.
The prison is nicknamed monster mansion due to its extreme levels of violence. It houses some of the most dangerous criminals including murderers and rapists.
Huntley was also attacked in 2005 by a convicted murderer who chucked boiling water over him at HMP Wakefield.