The killer of 11-year-old Rhys Jones is now locked up with some of Britain’s worst criminals after being moved to the “Monster Mansion” prison.
Sean Mercer, 32, has been transferred to the tougher jail - HMP Wakefield - while police investigate a suspected prison smuggling ring.
Fellow inmates at the brutal slammer, a Category A prison which was built as a house of correction in 1594, include black cab rapist John Worboys and Sarah Payne’s murderer Roy Whiting.
The switch was ordered after an alleged plot to smuggle in phones and other contraband was smashed at HMP Gartree, Leicestershire, more than 100 miles away.
Speaking to Sun on Sunday, a source said: "Wakefield isn’t a nice place to be — it holds some of the worst of the worst. It’ll be a real shock to Mercer’s system."
Mercer, who was just 16 when he shot Rhys, was ordered to gather his belongings in a top-secret operation.
When his cell at HMP Gartree was searched in a routine check last month, police started an investigation and a prison officer was arrested.
It's reported a stash of 12 phones, Sim cards and tobacco was found at his home.
Speaking at the time, a Leicestershire Police spokesman said: “Officers arrested a 26-year-old man from a premises in Gartree.
"The man was arrested on suspicion of conveying prohibited articles into and out of prison."
“He has currently been released under investigation."
Mercer was sentenced to life imprisonment serving a minimum of 22 years in December 2008, around 16 months after opening fire on rival teen gangsters in Croxteth, Liverpool.
Innocent Rhys was caught in the crossfire and the youngster was pronounced dead at hospital.
Four-part ITV drama Little Boy Blue based on the murder aired in 2017, and was largely met with positive reviews.
