When Peter Cameron was released from jail, after a long stretch for cannabis smuggling, he expected his phone to ring. He feared that criminal associates would seek to re-enlist him. 'There were people,' he says, 'who wanted to drag me back in.' Would he, Cameron wondered in his destitute, jobless state, be strong enough to resist? He says that if he had been convicted again, the court would have 'thrown away the key'.  He was contacted, but it was not the call he feared, but a retired judge - the late Stephen Tumim - inviting him to exhibit at the Discerning Eye exhibition at the Mall Galleries in London. It was an opportunity to transform his life that awaits tragically few ex-prisoners. Cameron sold four paintings and his life was changed for ever.  Before his arrest, the prospect of earning his living by painting would have seemed as unlikely as becoming an astronaut. In prison, he had joined a Spanish class but quit rapidly. The students ranged from South Americans who were fluent to illiterate Englishmen who could scarcely speak their own language. Art, by contrast, offered a level playing field. A tutor, Steve Best - cartoonist Bestie - spotted his potential: 'You've got a lot of porridge to do, so why not paint?'  Cameron did, and he proved to have a talent. Fellow cons lined up gripping family photos they wanted copied, a pastime for Cameron that proved a nice tobacco earner. Art also made the heavy years behind bars more tolerable. 'Prison is a dark world, where so many things are denied you. You cling to anything that will take you away from the drab, mundane existence,' says Cameron.  That might have been that had it not been for the legacy of a man familiar with prison's 'dark world'. Arthur Koestler, the author of Darkness at Noon, had not only been in three jails in separate countries - Franco's Spain, a wartime French concentration camp and our Pentonville as a suspected alien - but had been sentenced by the Spanish to death. Through his cell spyhole, he had watched others dragged before the firing squad.  In the 1950s, Koestler was a leading campaigner for the abolition of capital punishment. When that had been (almost) achieved, he turned his attention to jails. As an intellectual, he had survived by playing mind games; he set himself a 'timetable' - an hour for mental French, an hour for maths. But he knew the barren years most prisoners endure. 'The main problem is apathy, depression and gradual dehumanisation. The spark dies.'  He approached the Home Office, and was allowed to set up the Arthur Koestler Award (now Koestler Trust) to give prizes chiefly for art (but also for other creative activity) to prisoners, detainees and 'patients' in special hospitals such as Broadmoor. At first, he funded the prizes himself, and, when he committed suicide in 1984, he left £10,000. He told a friend: 'I wish a little cheap immortality.'  Koestler's name is still honoured. This week, the 45th exhibition of prison art opens in west London. There will be nearly 1,000 exhibits and prize money of £32,500, parcelled in small amounts to encourage the maximum number of artists. For many, a Koestler award is their first pat on the back; for a few, like Cameron, Koestler recognition is the gateway to a fresh start.  It is a high summer's day in what was the prison governor's house at Wormwood Scrubs in west London. The Victorian building is stuffed with art gathered from across Britain: paintings hang on every wall and every surface is stacked with ceramics, models, carvings.  Judges kneel, peer, compare notes as they choose works to be exhibited. The judges are professional artists and dealers and it is a strange potpourri that confronts them, ranging from work suggesting future Camerons to entries that seem to have strayed in from primary schools.  The winner of the portrait category, Endless Summer, is a painting of a young man's face uplifted to the sun against a clear blue sky. There is not a prison bar in sight. One of the judges, Nicholas Bowlby, a Kent art dealer, says: 'The face is very clever and has a lot of emotion in it - bewilderment, fatigue, yearning. Technically, the artist is seriously good, but he has something more than that.'  An entry from one high-security jail, entitled Prints Charles, is a portrait of the heir to the throne made (pointillist-style) of fingerprints taken from lifers. The caption reads: 'The inspiration came in some way by the anti-monarchist feelings of many of the working-class inmates who seemed to have a loathing for all things royal. Perhaps it was as a result of being in one of Her Majesty's jails.'  One artist, a contributor for years, always paints the Titanic. One picture shows the liner, having miraculously avoided the iceberg, arriving triumphantly in New York. Could this be a metaphor? What was the artist's own iceberg? Intriguing thoughts keep crowding in. An inventive contributor has made a model of a horse called Freedom's Quest falling at a steeplechase jump. The caption is 'Fall of the Quest for Freedom'. It is made from discarded betting slips.  Bowlby says that the works have 'an integrity, honesty and lack of artifice. It is as if, having been found out, the artists have nothing left to hide. The excitement as a judge is that you never know what awaits you'. Time, at least, is on the prisoners' side, hence the matchstick models of a grandfather clock, the Eiffel Tower and a mini-snooker table.  Amid the bustle is Jeffrey Archer, not as a prison artist but as a patron. For £40, he buys a ceramic plate by an inmate of Dumfries Young Offenders' Institution, showing a judge sitting above a barred window and a prisoner apparently drowning in the well of the court.  The next time I visit, Peter Cameron is there - he travels from Liverpool, where he has a studio, to help with admin work - and he tells of his redemption. Tumim, when both chief inspector of prisons and chairman of the Koestler Trust, had met Cameron in jail and offered to help him on his release. Many people make such promises and Cameron had put it from his mind. But Tumim delivered and organised Cameron's part in the Mall exhibition.  Cameron says: 'Without Koestler and Tumim, I would never have exhibited or been bought by influential people, never reviewed or written up. Prison artists get more attention than Slade students. Koestler saved me.' Some buyers of prison art are motivated by voyeurism - it's edgy to have an oil painting by a bank robber prominent in your kitchen. Cameron was once invited to speak at the annual show. Tumim was present, and Cameron's opening remarks brought the house down: 'Last time I spoke before a judge, I said two words and got nine years.'  The annual exhibition has been opened down the years by, among others, JB Priestley, Ludovic Kennedy, John Mortimer, Michael Foot and Rabbi Julia Neuberger, as well as by Joyce Grenfell, Willie Whitelaw, Terry Waite and (twice) by the Princess Royal.  Under the chairmanship of Lord Ramsbotham, Tumim's successor as chief prison inspector, the Koestler Trust has appointed a new director, Tim Robertson. The trust plans to develop the governor's house and urgently needs funds both for that work and to sustain the annual budget of £270,000, £45,000 of which comes from the Home Office.  Art is not on the official prison curriculum. And Ramsbotham, a retired general who, in his post-army career embraced the art of political persuasion, takes on all-comers when its value is challenged. He describes as 'crazy' a threat to the trust's government funding made on the grounds that in these target-obsessed days, it is impossible to measure the impact of prison art on reoffending. 'The arts are not an end in themselves, but a means to an end; they lead to work, education and training.'  Peter Fewell was illiterate when he went to jail. He had been raised in care, and spent his disrupted childhood 'fighting the system'. 'Teachers used to say to me, "You're an idiot; you'll never amount to anything." If you're told that often enough, you believe it. I decided that education wasn't for me.'  But a prison tutor said: 'You will be treated as a student.' 'I thought, "This is marvellous. This guy's genuine; he really wants us to learn." He made it fun and I was addicted.' Fewell became a wing 'scribe', writing letters for illiterate inmates. He heard about Koestler, but assumed he wasn't clever enough to enter. Eventually, pushed by friends, he won a short-story award. Two years on, as Fewell tells of the impact of that success, one can still hear the emotion in his voice.  As I left the governor's house, my eye was caught by a striking painting in a stairwell. Titled Never Ending Story, it showed red paint/blood seeping across a group of concentration-camp prisoners. Worthy of a prize, surely? Indeed it was; it had had two. One was hastily removed just before I saw the painting and the other several years ago. Apparently, a released prisoner had pinched it on his way out of Wormwood Scrubs and dumped it near the ex-governor's house.Assuming that it was an entry that had gone astray, the judges awarded it a prize and had set about seeking the artist when one of their number, a tutor at the Scrubs, spotted it as a past winner. It, if not the thief, was to be returned to the jail.  · The Koestler 2006 public showing is at St Mary Abbots Hall, Vicarage Gate, Kensington Church St, London W8 from Friday 22 September-Thursday 5 October (10am to 7pm; final day closes at 4pm). Contact the Koestler Trust at 168a Du Cane Road, London W12 0TX. Tel: 020 8740 0333; www.koestlertrust.org.uk
The Koestler award scheme, which has inspired prisoners for 45 years, is a testament to the redemptive power of creativity, says Robert Chesshyre.