A 'tornado' squad armed with shields and batons descended on HMP the Mount prison in Hertfordshire to quell riots that had broken out amid reports that two wings were "out of control".
The specially trained staff arrived at the Mount, in Bovingdon village near Hemel Hempstead, which is a category C male prison, at around 6.30pm on Monday night (31 July).
Sky News reported that the two wings affected housed 227 prisoners and that staff shortages as well as a "restricted regime" may have been behind the unrest.
Alex Cavendish, a prison affairs academic and blogger, told the broadcaster: "The technical term is that the staff have lost control of two wings. What 'lost control' means is that the prisoners are basically rioting, in layman's terms."
A recent report into the jail had said that violence and use of the drug spice were rampant, and adding to problems was a staffing shortage.
Mike Rolfe, chairman of the Prison Officers' Association, predicted last December that there would be an increase in jail disturbances as the prison service was in meltdown. There are concerns that government plans to recruit 2,500 prison staff would not be enough and that prisoner numbers needed to go down to stop jail riots.
Meanwhile in April, figures showed record levels of violence and a suicide rate that has more than doubled since 2013.
Mark Fairhurst, of the Prison Officers Association, told the BBC that staff shortages in British jails were a huge problem.
"We need to increase the starting salary to incentivise people to join and then we need to give them regular increments to incentivise them to stay," he said.
The Ministry of Justice said the incident at the Mount was resolved by 10.15pm.