BISHOPSTEIGNTON Probus Club members heard about prisons from an expert.

Stuart Leach, a prisons adviser, said the 85,937 prison population is kept in varying degrees of security according to the risks they pose.

The most violent prisoners have the tightest supervision, requiring as many as ten prison officers to supervise them as they are moved from their cell to the exercise area.

Prisoners who pose little risk spend most of their time in open prisons, with relatively little supervision. Nearly 3,000 prisoners at any given time are released on licence or home detention curfew, with only a watch-sized monitor on their ankles to check them.

Overall it costs £35,000 to keep somebody in prison.

The loss of liberty, rather than prison itself, is the real punishment, Mr Leach continued.

The days of extreme physical punishment and reducing food to bread and water as a punishment are long gone, but the subtle use of privileges as rewards and their withdrawal as punishment are very effective.

While televisions are available in cells, the programmes are available solely from the prison service and can be turned off from outside the cells. For a TV, prisoners pay about £5 per month deducted from their prison wages.

Mr Leach emphasised prison is an unpleasant environment with a strong smell of sweat, where violence is sometimes triggered among prisoners for trivial reasons.

Prisons cater for the full range of society, including Lord Archer – whose book comments on Mr Leach – and also cater for 44 religions.