The units can be built and rolled out at speed with a lifespan of around 15 years.

1,000 ‘Rapid Deployment Cells’ are set to be rolled out at 18 prison sites as the MoJ looks to accommodate the rising demand for prison places.

The first 48 such cells were unveiled at HMP Norwich yesterday – having been constructed and lifted into place seven months after the signing of contracts.

The MoJ has said the cells can be built and rolled out quickly – and have a lifespan of around 15 years.

They are reportedly being used to cope with demand while permanent capacity is being built across the prison estate.

Longer term work includes a £38m renovations of HMP Norwich’s Elizabeth Fry wing – which will create over 170 new cells by 2025.

In total £4bn is being invested to deliver 20,000 extra places.

Minister for Prisons and Probation Damian Hinds said: “We’re rolling out a thousand Rapid Deployment Cells to create extra spaces quickly while we press ahead with the biggest expansion of prisons in over a century – building six new jails and creating thousands of additional cells by renovating and expanding existing sites.

“The first rapid cells at HMP Norwich are already boosting capacity while our multi-million-pound renovation of the Elizabeth Fry wing will create long-term places to protect the public.”

Meanwhile custody cells are also being made available to cope with demand under Operation Safeguard. 

The Fed has already expressed concerns over the plans, saying last month: “If more prison cells are needed, they should be built, rather than relying on the police service to pick up more within their already overwhelmed workloads.”