Prisoners are obviously deprived of liberty, but other rights remain intact after they are locked up and, in particular, the authorities are obliged to keep them safe. In one case, a prisoner who fell over a slipper in his darkened cell during a power cut has won £3,750 in compensation.

The man had undergone hip replacement surgery shortly before the power outage and his mobility was restricted. During the time his cell was in darkness, he tripped on the unseen slipper and fell, hitting his head on a cupboard. He sued the company that ran the private prison, alleging a breach of the duty enshrined in the Occupiers' Liability Act 1957 to keep him reasonably safe.

The outage had lasted 37 minutes and, in upholding the prisoner's claim, a judge found that, had the matter been treated with proper urgency, the power would have been restored in about half that time. The prolonged lack of light in the man's cell was the direct cause of the foreseeable accident.

In challenging that ruling, the company argued that the judge had erred in failing to ask himself whether the cell was objectively unsafe and in imposing an unreasonably high standard of care. However, in dismissing the appeal, the High Court could detect no error of law in the judge's decision.