It may seem difficult to imagine but I spent 12 years and four months in Shanghai jails and have become a stronger, healthier and better man as a result. It took six years for me to come to terms with the complex situation I was in - the sheer magnitude of cultural change caused me terrible mental anguish. Can you imagine - all together in one enclosed environment - Korean, Japanese, Malaysian, Pakistani, Iranian, Nepalis, Myanmese, Singaporean, Australian, British, American and German prisoners, plus those from our host country. To this bewildering mix I added my own paranoia and anxiety. It was a culture clash from day one, often leading to conflict among ourselves and with the authorities. Despite this, none of us were mistreated during my 12 years' incarceration. I disliked many of the rules, especially those regarding remission of sentence, and the fact that there was no parole for foreigners. I had many confrontations with the authorities over such issues but they were consistently lost in red tape. Constant re-education rams it home that you should never forget who you are - a criminal. By simply examining why I was in the prison in the first place, I began to understand that the system isn't run to suit prisoners, it is a place of punishment - and suffer you will. I often complained about my rights but forgot to think of the rights I violated to earn time in the first place. It is easy to justify your wrongdoing with little phrases such as 'I only had cannabis resin, not heroin', or 'this was a class C drug non-addictive'. But in China an illegal substance is an illegal substance and carries either a severe prison sentence or the death penalty. The lesson is simple: don't visit other countries and break their laws - just don't do it. It is a painful yet somewhat profound experience to see someone being taken to be executed - some on a lesser charge than mine. It hurts to see that, but that's the law. I spent five years in Ti Lan Qiao prison in Shanghai which, ironically, was built by the British in 1903. There I began to realise that some of the guards' advice was at least worth trying in an attempt to correct my criminal behaviour. The Chinese system helps you confront your behaviour head on. Why did I try to smuggle cannabis? The truth is, irresponsibility and selfishness - it was so I could afford to continue my travels and carry on experiencing the shady side of city nightlife in a drug-enhanced state, contributing nothing but illegal earnings to the criminal economy. On a monthly basis I would write reports into a diary given to me by the authorities. I was advised to pay no attention to other inmates' complaints. I came to understand the wisdom in those words rather late, and many times found myself getting aggressive about someone else's problem. My attitude had to change. This is a process that continues today. It is hard to change but I had help from a few guards and a few Chinese inmates who pointed out my strengths as well as my shortcomings. Shanghai jails are known throughout China for their strong efforts at reform, so public and self-criticism was the norm. I recall, on entering Shanghai Qing Pu prison, the speech by the then warden Yu Zongming. He said the jail was modern and civilised with a strong emphasis on cultural values. Quite a statement. It was civilised in the sense that no one could raise a hand in violence without being punished and I experienced on more than one occasion the severity of the punishment cells. I was never mistreated, but the daily routine was difficult. Standing upright with a correct posture for an hour, then sitting with a correct posture for another hour from 6am to 9am for 14 days in any weather tends to focus the mind. The exercise is worthless unless you learn from it and make a change. I was a slow learner. Inside, art was my lifeline to sanity. Art fed me meditative ways to strengthen myself. Can you be honest enough to commit to canvas what comes into your mind? Can you be honest enough to portray that? Do you want to? Some things may be too personal. In short, art opened up doors in my psyche which I may yet explore and experience. I have always had a creative imagination, writing poetry, dancing and mimicking. Art was something I could do in a confined space. Materials were not easily available in the early days of my prison sentence so I scrounged around - after all I am a street urchin from Glasgow, where in the mid-1950s, as part of a hungry family, I begged on the streets like so many others. This helped me relate to the people in China. They were living in a land going through a major transition, in many ways still a third-world country. I put myself about, a bit of trade here and there - which, incidentally, didn't always go smoothly. But it was worth the effort and earned me enormous face from the locals. Just making down-to-earth-level communication was an art in itself - there are some very intelligent as well as mean folk in these places. At one point I wrote a request to buy art materials, which the authorities agreed to on condition I created reform propaganda posters. This I did and they were exhibited. After a few years the authorities asked me to teach classes. I had some sort of skill and most importantly I never missed a day from my easel, so I was considered reliable. I was happy to comply, and so, with three Africans and a Nepalese, I began to teach the other inmates. I can't point to one thing in particular that brought me to art and I don't see it as a way to earn a living, but it is something that I will always be involved in - I love it. The major turning point came when I began studying oil painting at Qing Pu jail. It fed my heart and soul, especially landscapes - what an adventure! When I began to try to express my feelings on canvas it was negative, or sexual frustration - what a profound experience to see your truth on canvas. What painting did for me was to help me discipline myself to sit eight or more hours per day at my easel. I discovered so much there that still gives me strength today. The inspiration you get is somewhat dulled by your surroundings, but you can create what you like from your imagination. It is a precious commodity in jail when you can bring a smile to families who receive such nice gifts from their loved ones, such as a portrait or flower garden. I usually did them for free because it was good practice. It was also a great means of escapism to explore landscapes, and the bodies of lithe Asian ladies whom I so dearly desired - after all, I was still a human with human desires. The time spent in prison in China changed my outlook on life. I am a positive example of the reform programme there.