A prison in Rutland is using a revolutionary flat-pack system to help ease the crisis of overcrowding.
The new wing will house an extra 120 inmates
The building at Stocken Prison near Oakham is made from steel-framed modules that bolt together like a construction toy.
It means that from next month the jail will be able to house an extra 120 prisoners in the new wing.
Andy Wilcox, a senior prison officer, said he was not worried about the security of the new building.
He said: "It's a very safe, very secure environment. The Prison Service have got it right this time - they've added all the facilities with it, the visits area.
"And at the end of the day people need to ask themselves if their son or daughter went to prison, would they like somewhere like this - safe, secure?"
The prison's governor, Steve Turner, said the new wing provided a much-needed solution to the overcrowding problem.
He said: "Overcrowding's been a serious problem for the Prison Service for quite some time now.
"Back in June of this year, we had 78 prisoners actually housed in court cells because we had no accommodation.
"The Prison Service is now meeting that need and building new accommodation to take up the capacity that's required."