More than 40 prisoners kill themselves each year, usually at the start of sentences they feel unable to face.
The scheme at Long Lartin prison in Worcestershire is the first in a Category A jail, although prisons with easier regimes have operated them. Swansea jail initiated the system, called Stressbusters, after the death of Philip Knight, aged 15, who was found hanged in his cell in July 1990.
Mike Haines from Cheltenham Samaritans, who helped to train the prisoners, says an outsider could not help as much as a fellow-inmate. 'We felt it was crucial that they do it themselves. We can't know what it's like to be inside.'
Josie Truscott, a psychologist at the prison, says 'listener' schemes are harder to operate in high-security prisons. 'There is a strong macho element here and a natural resistance to showing emotion. But the programme is working well.' Long Lartin inmates are all serving at least five years.
All eight of the prisoner-counsellors have full caseloads, sometimes seeing two or three men a week, but often the same person repeatedly for lengthy periods. The Stressbusters have been taught to read body language and recognise acute depression, and have weekly meetings with Samaritans to discuss any difficulties that arise.
Posters around the prison advertise the service, and the team wear T-shirts with the Stressbuster logo on. 'Initially, the Stressbusters were ridiculed and held in contempt by other inmates for their increased contact with prison staff,' said Ms Truscott, 'but that is stopping now.'
Leroy McKoy, 39, serving 10 years for drug dealing, says of the scheme: 'To be a good listener you have to not form opinions. We call it passive counselling, because it is not dictatorial. You have to revert the situation to yourself.'