HMP Millsike, a category C prison in East Yorkshire that opened in March 2025 at a cost of roughly £400m, has faced a turbulent first year and a half, according to seven former employees who spoke to a BBC investigation. The workers described understaffing, gaps in training and repeated call-outs of specialist response units to deal with serious incidents. Mitie, the private contractor that runs the jail, said safety remained its top priority and that operations were proceeding in line with plans agreed with the Ministry of Justice (MoJ).
When it opened, the government praised Millsike for setting what it called "the standard for the future" of prison design, pointing to its focus on rehabilitation and education. The facility was the first of four new prisons intended to help deliver a pledge of 14,000 additional prison places across England by 2031.
How many prisoners are currently held at Millsike?
The MoJ says around 1,100 inmates are currently housed at the site, though separate reporting suggests the true operating ceiling may be even more constrained. According to the Yorkshire Post, the prison has been operating at a restricted capacity of just 1,158 places, with hundreds of cells left empty because staffing shortfalls have limited how many prisoners can be safely accommodated. A separate report from the Telegraph put the number of unoccupied cells at 344 as of last month, noting the prison had reached an operational ceiling of just over 1,100 inmates — well below its full designed capacity. Mitie's own listing describes Millsike as a 1,468-place resettlement prison for men, according to MarketScreener, underlining the gap between what the site was built for and what it has so far been able to run.
What have former staff said about conditions inside?
Six of the seven former employees interviewed described chronic staffing shortages, and four said they had felt unsafe while working at the prison. All but one asked not to be named. Several raised concerns about colleagues' lack of relevant experience, saying some recruits had previously worked in supermarkets or fast-food outlets rather than in custodial settings.
The BBC understands that all operational staff at the prison undergo more than eight weeks of training, including periods shadowing staff in other prisons. The MoJ has said Millsike is expected to employ about 600 people, though it remains unclear how many of those posts are currently filled, since private prisons — unlike publicly run ones — are not required to disclose staffing data. Mitie declined to specify the number of vacancies when asked.
At a public meeting held in June, interim prison director Paul Newton reportedly told local residents that recruitment had been difficult, and that around 90% of employees had no prior experience working in the prison sector. Mitie responded by saying that recruitment and training had been "aligned to the prison's phased growth" and that it draws recruits from other backgrounds, including the military and wider parts of the criminal justice system.
What incidents have occurred inside the prison?
Three former staff members who worked in non-officer roles said the shortage of trained prison officers meant they had been asked to carry out duties outside their job descriptions — including "bed-watching" prisoners considered at risk of self-harm, despite having no training for the task.
Steve Richardson, who worked in maintenance at Millsike for ten months, was among them. He said inmates had thrown faeces and urine at him, and that staff had frequently had to "mix in" and support one another to cope. Richardson also said he was never given control and restraint training, known within the service as DoJo training, which is designed to help staff manage violent confrontations. Mitie said everyone who required DoJo training had received it.
Richardson recounted a night in November 2025 involving a serious disturbance:
"absolutely lost it and he started throwing pool balls and cues around"
He said the inmate smashed six windows and attempted to climb a perimeter fence before a specialist squad from the Operational Response and Resilience Unit (ORRU) intervened. The ORRU comprises specialist teams, including a dog unit, and is deployed for the most serious high-risk incidents. Data obtained by the BBC under a Freedom of Information request shows ORRU units were called to Millsike seven times over nine months in 2025.
By comparison, other privately run category C prisons for which data was obtained saw fewer call-outs over a similar period: units were deployed eight times to Oakwood, and three times each to Fosse Way and Northumberland. Mitie said the frequency of call-outs at Millsike was in line with expectations.
A sewage pumping station at the prison broke down in November 2025 amid reports that inmates had flushed clothing down toilets — a claim Mitie has denied. In June 2026, a female prison officer was given an eight-month suspended jail sentence after admitting to having a relationship with an inmate.
Have safety concerns been raised through formal channels?
In a separate incident on 9 July, residents living near the prison reported seeing a bomb disposal vehicle enter the site, followed later by a loud bang. Messages sent by inmates that evening, seen by the BBC, referenced alarms sounding and the noise of an explosion. Humberside Police and Humberside Fire and Rescue Service confirmed they attended alongside an explosive ordnance disposal team. Mitie said no viable device was found and that emergency services had attended in line with standard procedure.
In January this year, the Independent Monitoring Board (IMB) responsible for overseeing the prison raised its own concerns about safety and security. Its report noted that board members had taken to visiting the wings in pairs because they felt unsafe doing so alone, and had observed doors and gates left open. The following month, the prison's director, Samantha Pariser, was replaced; Mitie said she had moved into a "new strategic role" within the company.
Was the prison opened too soon?
Concerns have also been raised about shortfalls in education and rehabilitation provision, with former staff describing attempts to run sessions without sufficient equipment. Joe Chapman, a former prison officer who has not worked at Millsike himself, set up a support group for prisoners, their families and staff in response to what he called a chaotic start to the jail's operation. He said he believed the prison had been pushed into opening far too early by the government.
"Where I think Mitie have gone wrong is by not being transparent with prisoners, their families and even with their own staff about the difficulties they have experienced,"
"They are trying, but at this moment in time, in my opinion, failing."
The Prison Reform Trust said it had received calls from prisoners at Millsike raising concerns about their safety, though its chief executive, Pia Sinha, said this was not unusual for a new prison. She described some of the calls as "worrying and concerning" and said the trust had raised safeguarding issues directly with the prison, which had been responsive. Sinha noted that some of the difficulties Millsike had faced were similar to those seen at other newly opened prisons.
"We do need to cut them a bit of slack because it takes time,"
Mitie said it maintained "a safe, secure and supportive environment for prisoners, colleagues and visitors" and reiterated that safety was its "highest priority". PeoplePlus, which delivers rehabilitation and education programmes at the prison, said:
"Education and industry services have developed in step with the prison's population."
The MoJ described Millsike as "a vital part of our plans to build 14,000 new prison places", adding that "a robust procurement process" had been carried out before the contract was awarded to Mitie, and that it would "act when standards fall short".
What is the prison's background?
Millsike sits alongside the existing HMP Full Sutton near York, according to a government announcement issued when it opened, which also noted the site takes its name from the nearby Millsike Beck. It was the first of four new jails intended to help meet the government's target of creating 14,000 prison places by 2031, as set out in a separate official statement marking the arrival of its first prisoners. The jail is operated day-to-day by Mitie Care & Custody and is located at Full Sutton, York, YO41 1FZ, according to Mitie's own prison information page. The MoJ has said the prison's modern construction, which includes solar panels and heat pumps, is expected to save around £1m a year in running costs.
What happens next?
An annual report from the Independent Monitoring Board, expected to be published within the next month, is set to address the safety concerns raised during its visits. Mitie's own published visiting schedule shows the prison continuing to operate normal weekly visiting sessions, with no visits held on Mondays and fixed slots running through the rest of the week and into the weekend, according to Mitie's site listing. Whether the prison can move beyond its current staffing-constrained cap and open its remaining empty cells is likely to depend on further recruitment, a point underlined by the Yorkshire Post's reporting on the hundreds of places still sitting unused.
Key Facts
- HMP Millsike opened in March 2025 at a cost of about £400m and was designed to hold up to 1,500 prisoners.
- Around 1,100 inmates are currently held there, with reporting suggesting the prison is operating at a restricted capacity of roughly 1,158 places and as many as 344 cells left empty due to staffing shortages.
- Specialist ORRU units were called to the prison seven times over nine months in 2025, more than at two comparable privately run prisons.
- Director Samantha Pariser was replaced in February this year; Mitie said she moved to a new strategic role.
- An IMB annual report addressing safety concerns is due for publication within the next month.
