BRITAIN’S workplace safety watchdog is preparing to formally reprimand His Majesty’s Prison and Probation Service over dangerous radon exposure at HMP Dartmoor, after investigators found staff and inmates were subjected to illegal radiation levels for years.

The Health and Safety Executive (HSE) announced it intends to issue a Crown Censure – the toughest sanction available against a government body – following a major investigation into conditions at the Devon prison.

HSE said it was first alerted in February 2023 after HMPPS reported suspected overexposure to radon, a naturally occurring radioactive gas linked to lung cancer. Monitoring later confirmed that radiation levels in parts of the prison, including prisoner accommodation blocks, exceeded legal safety limits.

Inspectors concluded that both prisoners and prison staff were exposed to “significantly” elevated radon levels over a prolonged period, raising serious concerns about failures in risk management and workplace safety compliance.

The watchdog took enforcement action twice in 2023, citing breaches of radiation safety regulations in February and again in December. HMPPS later decided to mothball HMP Dartmoor in 2024.

Following the investigation, HSE’s legal services division reviewed the case and authorised a Crown Censure under the Code for Crown Prosecutors. While not a criminal conviction, the move is equivalent to approving criminal charges against a Crown body.

A formal hearing will now determine whether the censure is confirmed. If upheld, it will stand as a permanent public record of HMPPS’s failure to comply with health and safety law. No financial penalty can be imposed.

Radon is the second leading cause of lung cancer in the UK after smoking, contributing to more than 1,000 deaths each year. Parts of Devon, including Dartmoor, are known radon hotspots because of underlying geological conditions.

No further charges are being brought against any other organisations or individuals connected to the case.