In the early 1950s I went to work in the Sudan, long before the present problems had arisen in the country, to improve the grazing for the cattle-owing tribes - the Baggara - who lived in the southern parts of Darfur and Kordofan provinces. It was necessary for my work that I lived with the tribes - the Rhizeigat and the Misseiria - and for a year I lived in a grass hut just outside the village of Abu Mutariq in Southern Darfur, a community of perhaps a thousand. Apart from me, the village consisted of solely Sudanese, mainly Arabs.

The civil powers in that region where vested by the central government in the head of the tribe - the nasr - who lived in Ed Da'ein, a larger town about 50km distant. He exercised his authority through the local sheikh and a policeman, Beshir, who lived in the village. Although I call him a policeman, he did not wear any uniform but, such was the extent of the powers vested in the nasr and the strength of his rule, that the policeman, his representative, required no outward sign to exercise his authority over the community.

I did not have a lot to do with Beshir, but we always had cordial relations. I liked him and I expect I was a novelty to him so whenever we met we went through the long ritual of greeting, as is the custom in Arabic countries.

After I had lived in the village for several months, I heard that Beshir had been taken ill and, later, that he had contracted leprosy. Since ancient times, people have been horrified by leprosy and the disfigurement of face and limbs which it caused. They were also terrified of lepers as it was believed that the disease was so contagious that even the mere touch of a leper was sufficient to contract it. The reaction throughout history has been to isolate lepers - on islands, in distant colonies, far from their families - to prevent the spread of the disease.

I was horrified to hear that Beshir had this disease as I expected him to suffer the typical loss of fingers and toes and mutilations of his facial features. He had left the village and gone into isolation and I did not expect to see him again, as medical facilities in Southern Darfur were rudimentary.

And so it remainded until shortly before I left the village, when I was surprised to see him one day walking around. He seemed much the same although he had his hands hidden inside his jallabah. My colleagues told me that he had now returned to his duties as he had been cured of his leprosy. I had some reservations about this as it seemed to me to be a very short period in which to be cured of such a serious disease. However, he had seen me and, to my consternation, advanced towards me with hand outstretched to greet me. What would you have done?

I am glad to be able to report that, with only a moment's hesitation, I grasped the man's hand and shook it. We talked. But when Beshir had walked on, I went swiftly back to my hut and thoroughly washed and disinfected my hand!

Some years later while watching The Motorcycle Diaries about the journey of Che Guevara through South America, I noticed that he was confronted with the same dilemma. He responded in the same way as I did and shook the man's hand. But whereas he, as a medical student, did it out of courage, I fear that my action may have been the result of cowardice - the fear of an Englishman to create a fuss.

Later I found that my consternation was groundless. Contrary to popular belief, leprosy (or Hansen's Disease as I believe it is now called) is one of the least contagious diseases. But neither Che nor I knew that at the time!