“They got him on a Saturday, which is generally quieter, with less staff on, and it seems to have been planned.”
His injuries were initially reported as life-threatening, but West Yorkshire police have since said that is not the case.
The attack was reportedly sparked by Watkins giving guitar lessons to inmates and jealousy over him receiving visits from his younger girlfriend.
Watkins, 36, pleaded guilty in 2013 to 13 charges, including trying to rape a baby, sexually touching a 1-year-old, encouraging a fan to abuse her child and making child pornography.
Judge John Royce called Watkins a manipulative and dangerous sexual predator who had abused his fame to help satisfy his “insatiable lust”.
“Those who have appeared in these courts over many years see a large number of horrific cases,” Royce said in sentencing at Cardiff Crown Court in 2013.
“This case, however, breaks new ground.”
Two female accomplices, described by prosecutors as “active participants in the most shocking abuse of their own children”, were jailed for 15 and 16 years respectively.
Lostprophets — which formed in 1997 and had a chart-topping album in 2006 with Liberation Transmission — disbanded after Watkins’ initial arrest.