Prison chiefs are trying to prevent violence behind bars by painting the walls soothing colours. England’s newest jail, which is the first to be partly built by prisoners, has a mix of “autumn” colours inside the wings and the housing blocks are painted in a magnolia-style colour dubbed “warm truffle”.

The cell doors at HMP Millsike are painted orange and the furniture was a mixture of greens, blues and purples. The Daily Express was among the first visitors to the Category-C institution in North Yorkshire and heard how justice chiefs are trying to create a more “calming” atmosphere for inmates. They even relied upon academic research on the best colours for the walls and floors, amid a violence and overcrowding crisis behind bars.

Assaults behind bars are up 18%, with 29,881 incidents.

Of these, 3,318 were considered “serious assaults”. This figure was also up by 17%.

Attacks on staff have also increased by 23% to 10,496, shocking Ministry of Justice figures revealed.

And Justice Secretary Shabana Mahmood said: “We have a duty of care to our prison officers and all of the other staff that work here to maintain a safe environment.

“So, some of the design features are to keep a calm environment so that you don't have prisoner on prisoner violence, but also so you don’t have violence against members of staff either.

“Everything here has been tested to try and create the best possible environment to help offenders engage with the rehabilitation activity that is necessary for us to ultimately cut crime.”

Prisoners will be allowed to choose the first names of the cell blocks, in a bid to make it feel more like a “community”. And they will be able to form a small committee to have a say on how the institution is run.

The convicted criminals will be able to apply to tend on-site allotments “so they can grow their own vegetables and flowers”, a site manager said.

Even the security arrangements are designed to make it feel less like a prison. Scanners are made to look like “airport” metal detectors to prevent visiting children from becoming scared.

When family members arrive, inmates are able to sit with their loved ones in a large patio area connected to a children’s playground.

Insiders believe this will establish a stronger family link that could prevent reoffending.

The £400million prison, on the outskirts of York, is also the first to be built by serving prisoners. The Ministry of Justice revealed 44 people released on temporary licence and 40 prison leavers were involved in the construction of the facility, which will be able to hold up to 1,500 inmates.

The prison has roughly 1,850 CCTV cameras that cover every inch of the estate.

And the glass used for the windows can sustain a direct “attack” for at least 90 minutes, justice chiefs believe.

The first inmates are expected to arrive at the end of April.

Inside F-block, one of the six housing cells, they will be able to enjoy a pool table, table football, and table tennis.

The layout of the block – effectively a cross – is such that prison staff will be able to see offenders coming in and out of every cell.

And as they walk to workshops and training centres, where they will learn skills they could use when they are released from prison, the convicted criminals are met with motivational messages – including one from Dolly Parton.

It tells inmates: “If you don’t like the road you are walking, start paving another one.”

Justice Secretary Ms Mahmood admitted: “Millsike is also designed to get offenders to turn their backs on a life of crime.

“Yes, prisoners must be punished – on that, I have always been clear.

“But prisons must rehabilitate too. Prisoners at Millsike will often be at the end of their sentences and they won’t be able to idle away their time away here.”