Maghaberry high-security jail in Co Antrim holds life prisoners convicted of the most serious offences including murder and paramilitaries.
Many struggle with substance abuse, self-harm, lack of education and poor mental health and some are extremely vulnerable.
In April watchdogs revisited the institution three years after finding it “unsafe, unstable and disrespectful”, and said excellent leadership efforts to stabilise it had borne fruit.
The inspectors said: “We rarely see a prison make the sort of progress evident at Maghaberry and it is to the credit of all those involved that many of the outcomes for the men held at the prison are now among the best we have seen in this type of prison in recent years.”
Levels of violence and disorder had reduced significantly and the prison was much more stable and calm, while relations between staff and prisoners had been “transformed”.
Areas where inmates congregate were once no-go zones for staff but are now regularly patrolled.
Reservations remain over the handling of vulnerable prisoners, the inspectors said.
Five inmates have killed themselves since the last inspection and a “very high” 500 reports of prisoners at risk had been opened recently.
Observation cells for inmates vulnerable to self-harm had been used 200 times and strip clothing, designed to be resistant to suicide bids, in 80% of cases, which inspectors noted can add to distress.
The unannounced inspection was conducted in April this year by Criminal Justice Inspection Northern Ireland, HM Inspectorate of Prisons, the Regulation and Quality Improvement Authority and the Education Training Inspectorate.
It said the regime inside was much better than observed previously and was being delivered reliably.
It also said learning, skills and the provision of work had improved but much more still needed to be done.
The inspectors said rehabilitation and release planning work was amongst the best they had seen.
Prisoners received good support on arrival, a special area is set aside for the first few days with arrangements for mentoring by other prisoners and enhanced contact with family and friends, and the prison seemed safer, with a relatively low level of violence but many men still said they felt unsafe, the report said.
Robust and effective action had been taken to reduce the supply of illegal drugs.
Some men spent long periods in a special care and supervision unit but more was being done to integrate them, inspectors said.
Levels of self-harm had fallen but management arrangements were too risk- averse, which can mean over-reliance on intrusive monitoring which can itself be stressful, and the underlying issues were not addressed adequately, the review found.
The response to recommendations following deaths in custody was “insufficient”, the report said.
At the time of inspection there had been five self-inflicted deaths since a previous inspection in 2016.
Living conditions were reasonable, although some “houses” offered poor cell accommodation, the inspectors said. A new block is being opened soon.
A more conducive environment for training and learning was created but inspectors said not enough activity places existed and the curriculum was too narrow.
Attendance records needed improvement. Long waiting lists were noted for more popular courses. Outcomes were not sufficiently good.
Release from prison planning and outcomes for prisoners were good.
The report made 14 recommendations surrounding the negative perceptions held by many prisoners, the need for timely responses to health complaints and poorer outcomes seen by Catholic inmates.
It said the practice of supplying medicines which had been prescribed for direct administration by prison staff should be reviewed to reduce the opportunity for bullying by other prisoners.
Prison Service director general Ronnie Armour said: “This latest report demonstrates the huge progress which has been made at Maghaberry Prison.
“From a facility which was described in 2015 as ‘unsafe, unstable and disrespectful’, criminal justice inspectors are now reporting ‘progress rarely seen’ with ‘outcomes for prisoners now among the best’.”