Rye Hill Prison 'must do more to stop grooming' by inmates
Staff at a jail which houses more than 600 sex offenders must be more alert to the risk of prisoner-on-prisoner sexual grooming, an inspection report said.
Rye Hill Prison, in Northamptonshire, had "real strengths" but must do more to stop inmates, especially younger ones, becoming victims, the report said
Governor Richard Stedman said it would be "naive" to think offenders lost the ability to "manipulate" once in jail.
But he said his staff were getting better at dealing with the problem.
The Category B prison switched in 2014 from housing a mix of offenders to only those convicted of sex crimes.
The report said it was overall "performing very well" - it was safe, with bullying generally well managed, and the cells were in good condition.
It said staff "were generally aware of the particular risks associated with the sex offender population".
"But there was no strategic approach to ensuring that all staff were aware of the potential for prisoner-on-prisoner sexual grooming and targeting, especially in relation to some of the younger prisoners held at the prison."
Rye Hill holds some of the most dangerous sex offenders in Britain - 90% are serving sentences of 10 years or more.
Mr Stedman told BBC News: "We now have a population that is much more sophisticated and able to manipulate and condition because, let's be honest, that's how they've been able to commit a lot of their offences."
He said many inmates had committed offences against children, adding: "It would be really naive to think those behaviours disappear when they come into custody.
"They don't have access to children so they will often focus their behaviour on staff and their peers.
"I would recognise that we've had a lot of learning to do when an establishment changes in such a short period of time. It takes time to learn about those behaviours, so we're getting ever better."
Healthcare services were also judged in need of improvement, with staff shortages and long waiting times for most clinics.
Chief Inspector of Prisons Nick Hardwick said: "This was a positive inspection and HMP Rye Hill has some real strengths.
"Its purposeful activities, and offender management, both vital for this population, are better than we normally see and there is much that other prisons can learn from this.
"Nevertheless, in some other areas, particularly healthcare, the prison was not meeting the needs of its population and these areas now needed to be brought up to the same standards as the rest of the prison."
Michael Spurr, chief executive of the National Offender Management Service, said the report showed Rye Hill was "a decent and safe prison", but staff would work hard to improve in the areas highlighted by the report.